As far as cleaning goes you've got the right idea, a brush is best so as not to wear the plastic. If they're still wet then don't be afraid to give them a good rinse first, maybe wash them with ammonia to disinfect and hit them with a blow dryer, but not so close that they'll melt!
Replacement stickers can be found for many figures at
ToyHax.
Screws may not be salvageable, but if it's only light rusting try to remove them, get the rust off with a brush, and seal them with a
clear metal sealer on the head so they don't rust back up.
Hope that helps.
Emerje