The only thing that gives me trouble in MM2 is the third boss in Wily's Castle, where you have to use the crash bombs. I end up running out of crash. The strategy I always used was to go in, destroy all the walls, die, refill the crash meter and go back and destroy the targets. I also use the trick where you can make bullets pass through you by pausing and unpausing. I haven't played MM2 in a long time, I'd probably be too impatient for that now and try to beat that boss in one try.
You know, I think I'll go play Megaman 2 now.