If a cock is involved: snowballing, two people giving the third a blow job together, someone giving a blowie or having penetration with the cock and the other making the cock-haver perform oral. If it's all cocks or at least two involved, one guy lies back and has his partners penetrate him with the other rides him.
If there's vaginas: train of people getting eaten out/use of a strap-on, lot's of toys used, rubbing on each other to get off while the third watches (of gets fingered by a fourth).
Eldritch horror genitals/xeno: Creature has genitals that lets them fuck multiple people at once (tentacles, multiple genitals, ect).
In general, having the third (+fourth) watch or narrate for a while before the other two pounces on them when they get too overwhelmed is always nice.
Re: Prompt help - threesomes/foursomes
If there's vaginas: train of people getting eaten out/use of a strap-on, lot's of toys used, rubbing on each other to get off while the third watches (of gets fingered by a fourth).
Eldritch horror genitals/xeno: Creature has genitals that lets them fuck multiple people at once (tentacles, multiple genitals, ect).
In general, having the third (+fourth) watch or narrate for a while before the other two pounces on them when they get too overwhelmed is always nice.