One of the best ways to jack off with buddies is to put porn on the TV and add alcohol to drink. Then a comment about "I am so horny I think I'll get out of these clothes and jack off" can sometimes start the session. You do run the risk that you might be the only one jacking off, put it may put an idea in there head about doing it the next time. Another idea is to invite them over but be in a towel or robe with nothing on underneath like you just got out of the shower. Just don't get dressed and if possible have a porno playing on the TV when they come in. Offer something to drink and make small talk about the porno and then steer the conversation to sex and things you like or what is going on. Let your towel or robe fall open and casually start to play with your cock. At some point, leave the porn running, and go to the other room to give the other guy or guys time to get their cocks out while you are away and then sneak back in and finish jacking off together. Good luck