1. Get tispy
2. Bring up the topic of sex to get him turned on.
3. Ask about porn, porn stash and show him some of your favourite porn online. If he likes it then wait for a few minutes so he is totally horny from the porn then start stroking yourself through your jeans, if he doesn't mind after a few more minutes then whip it out and make sure to look confident that way he will join too. (someone has to lead the way and you are the one who's goal is to have a mutual wank so its up to you)
After this he probs will be fine and he may lead the way.
If he is not reacting to your porn ask him to show his porn instead and see if he is turned on from that then proceed. BUT if he is not looking interested or horny at that stage then don't go any further.
Just jokingly blame it on the drinking the next day to avoid awkwardness if it goes bad or if it goes good then don't talk about unless he brings it up and wait for the next time
( For the law: Just remember to be safe and respect others boundaries if they decline)