Along with oil on the top, rather than taking the BB off, unscrew the little water bottle bolts, flip the bike upside-down, and spray WD-40 (with the little red straw WD-40 cans usually come with) in the holes. Then do as above with the seat after a few days of this (leaving it to sit overnight). Perhaps use a crap old seat to avoid bending the rails on the one you intend to actually use.