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Briefly, pants are rolled up to the knees, and the upper part, along with underpants, lowered to the knees (you don't want them around your ankles!). Items capable of falling are best removed beforehand; retrieving them will likely be impractical. You squat by first bending the upper part of your body forward (to maintain balance), then lower yourself by bending your legs, coming to rest quite naturally (and comfortably) on your haunches and legs. Reverse to rise.
Aim is more important in squat toilets than in sit toilets, so don't fire indiscriminately.
Cleaning up in most places will likely not involve toilet paper, unless you brought your own. This is done using a (probably nearby) container to bring water to your waiting left hand, which will splash it on the appropriate areas.
If you do use paper, do not deposit it in the toilet (unless there's no plumbing involved), or you will probably clog the pipes. There is likely to be a wastebasket handy: the soiled paper goes there. Yes, really.
Seko Packing List - Health :: One Bag