I’d REALLY like to tell you this will be easy, BUT I can’t! The BEST way to do this is to scrape all the loose crap off the walls. Have the Aleve handy!
>>> If you just repaint over this mess, your new paint might just tear off some of the older layers as it dries!! In effect, your new paint would barely be clinging to a shaky surface. Paint HAS to be applied to a clean, sound, & PRIMED substrate to look and perform it’s best.
>>> After you’ve gotten down to the “sound” paint layer, wash the walls with a TSP cleaner, rinse well, let dry, and PRIME the wall with a top-quality primer. This is SO important for good adhesion & eveness of the sheen.
>>> If there’s any wall repairs to do (gouged paper, nail holes, etc.), do them B4 you prime.
>>> Use the appropriate SHEEN of paint for the room(s): SEMI-GLOSS for a main bath, SATIN for a kids room, entries, kitchens. TWO coats are necessary over the primer.
>>> If you’re doing a deep red, use a gray primer, & 3 coats of red.
Good luck!
Faron