Sorry, if you talk about the size of your penis or try to indicate in any way that you're well endowed, except as a joke that is clearly intended purely an attempt to get others to laugh (and you don't act like your joke is meant to be taken seriously), then you will look like a big dick yourself, instead of a stud who has a big dick. Women aren't impressed by men who talk about their cocks or who boast about their sexual performance.
That's good advice in my opinion.
I actually have a friend who claims to be large. Even whipped it out once in front of me and another guy friend but we turned away before really seeing it and were just like "What the fuck!?" We never told anyone else or spread the word because the fact that he was trying to show us was just fucking -weird-, as much as I love the guy as a close friend, lol.
One time we were out and he started talking about how big his dick was, and was and then put his girlfriend on the spot and asked her to admit he was big, the conversation grinded to a halt and even she was like "What the fuck do you want me to say?" Then he goes on and is like "You don't understand, I know I have the biggest out of our group."
So finally I just go, "Really? How do you know? Because you know, even when I was a baby and female family members would have to change my diaper, they still tell me about how big I was... and you know what? I still have a big dick to this day... for a baby." (Which I said, even though I'm average, and not small, but just for laughs)
People laughed, he just looked weird, and we all changed the subject totally uninterested, much to his disappointment.
So, if you're that big and that good, word will get around on its own. If you deserve a reputation, you'll get one, and then put it to use. Don't try to force one for yourself.