I have a very thick cock, and it was a long time before I learned how to top properly. When I had dates, etc., the act usually ended in frustration and disaster. Trouble getting it in leads to loss of confidence, which leads to a softening dick, which compounds the problem. I never understood what fucking should be like. Failure to perform spoils the evening or more, as does trying too hard and causing injury.
For me, part of the problem and solution was needing gain confidence with bottoms who are experienced with taking a large cock first, and then eventually learning how to prepare those who aren't. My breakthrough came when I met people who were extremely experienced with big girth--my friends started holding regular fisting parties, and for the first time I found men I could penetrate easily, men who regulatly took someting wrist-thick, and who could take a good fucking with big cock. That gave me confidence, I decided I liked fucking, and eventually learned how to do it with others without such extreme experience. But not everyone can take it, even with better topping technique.
The anus and rectum are muscle, and need to be relaxed and conditioned for what is to enter. Some bottoms use poppers to help relax the muscle. While I don't like them, and don't condone them, I have to admit they really helps some guys open up. But physical stimulation can do much the same, particularly when done at the same time as erotic play. Lubrication is important, not just on your cock, but also inside (something else I learned at fisting parties).
So embrace and kiss. Touch his erogenous zones. No, they are not in his crotch. Many are on the head, the ears, earlobes, back of the neck. Stroke between the thighs. Then maybe, when he's ready, touch his cock a little, but not too much. Believe it or not, such stimulation does loosen the hole, even for tops. Then while still embracing, touch his hole. Get a feeling for how tight it is. If it's nowhere close to being able to take you, lube your fingers very well, and gently work in one. Work the lube inside. Stimulate him inside, not too mcuh, but gently and playfully. Then a second finger. And then a third. For me, it was three well-lubed fingers and feeling him start to relax around them that signaled he was ready to try my cock. Work the head in gently, then pause. If he's still tight, don't try to long-stroke immediately. Just do a little in-and-out, like half an inch, to let your cockhead stimulate the inside of his hole. You can do this even if you're not rock hard, as the pressure of insertion may have softened you a bit. Just support your shaft with your fist. You'll harden up again soon. As you feel him loosen in response, push in a little further, but still limit yourself to short strokes. You're not trying to fuck yet, just getting his hole relaxed. Add lube as necessary. Sometimes, you need to pull out and start over. One you have worked in maybe two-thirds of your cock, start longer strokes for a while. The push in further then you were before, and try to open him up deeper. If this seems painful to him, back off of that depth, and try again later. Learn how to distinguish his body language, grunts, and moans to tell the difference between "Hurts too much," "Hurts, but in a good way...open me up!" and "Damn that feels good, no one ever hits that!"
Another helpful method, if he's into toys, is to have some dildo play first, possibly working up in size. Personally, I don't like to use toys, but for many guys they work. I often go to sex parties, where some bottoms take a different approach... "Let me get fucked a few times first, they I'll give you a try." It worked wonders last Saturday night...
With patience, I've had guys go from seemingly impossibly tight to getting pounded hard with full-length strokes in a matter of time. But everyone has their limits, and sometimes it just won't work. If it's at something like a sex party, you both just move on. If it's a one-on-one encounter, have a plan B. Maybe he'd like to blow you big cock, while you finger him, or whatever might salvage the situation. NJust don't crumble under feelings of inadequacy-- remember, you have this problem because you are big. Other guys tighten up, like crushing your cock tight, when they get overstimulated. You need to learn how to read your bottom and slow down until he's ready for more, not give up.
Be sure to keep everything well-lubed, adding more as necessary. And use good lube. Much of the stuff sold as sex lube is complete crap, and either isn't particularly slippery to begin with, or looses it's slickness quickly. My personal favorite is Wet Platinum Silicone lube, but there are other good ones, too. Water based lubes, in my experience, don't work well, because the wetness (water) gets absorbed into the body tissues quickly, and the lube gets gummy and looses effectiveness. Oil-based lubes also exist, but I don't use them. Both silicone- and water-based lubes are compatible with condoms, while oil causes the condom to break down.
If you use condoms, also make sure they fit correctly. Do not believe the utter bullshit videos where someone stretches a regular condom over their head, a watermelon, their foot, or whatever, and says "If it fits that, it fits any cock." Those are made by people with small dicks (and often women), who have no idea of the problem. If the condom compresses you cock in an unnatural way, you will have trouble staying hard. Many "larger" condoms are just longer, or wider at the head only, but still narrow at the base, and simply don't work for men with thick cocks, particularly when thickest at the base. There are specialist condoms available on-line with better sizing, and many allow you to select the proper fit by measuring your cock (length and girth) with a little paper gauge, and then choosing the best-matched size, just as you would for trousers.
In interest of full disclosure, I will admit that I seldom use condoms these days. Given PreP and some selectivity in who I fuck, I now prefer bareback. This also give me more stimulation, which at my advanced age is helpful. However, I used to be the poster-boy for condom use, and please, if you are just starting out with sex, and haven't yet developed judgement and experience, use a damn rubber!
By the way, don't worry about not cumming. I usually don't cum during the act either. I do enjoy watching my bottoms get off, and sometimes cuddling afterward the time is right, and I stroke out a load for them. Some bottoms think it is their duty to make the top cum first, but just explain that they'll get their reward later.
