To us, foreplay is sex as much as intercourse. We can't imagine just "f-ing" without also kissing, touching, oral, and everything that makes sex great. We do it all. We don't even think of it as "foreplay", because all of these things occur throughout a sexual experience with somebody else, are interchangable with intercourse, and we could even finish with "fore"play. Our preference is for longer, more sensual experiences. We also like group sex with another couple, all kinds of interactions going on (not just M/F M/F). People who just want to get in a room and bang for an orgasm, as little foreplay as possible, aren't our type.
The only thing I can think of that differs with swing partners, is that we use condoms with them for intercourse. Also, we don't want other men to cum in my mouth. This is for safety concerns.