How do I paint and fix peeling paint and hairline fractures on my indoor concrete (cinder block) walls? The popcorn ceiling is a mess too.
Alkali resistant mesh tspe, 1 m wide, embedded in a modified (latex plasticizers, usually) mortar that you would skim coat over fine cracks.
This will also cover larger cracks, if it is stable (> 1 yr).
Use a stiff wire brush or wire wheel to prep. Use any recommended surface bonding liquid.
You have to determine if moisture is playing a role first. Tape a one-square-foot piece of Saran Wrap to the wall in a few places and leave them there for a month or so. Check them occasionally, especially after wet weather, to see if any moisture has developed on the plastic. If it's wet, you have to address your moisture problem before wasting your time on painting a wall that won't hold paint.
Once the wall is waterproof, caulk you cracks with the best paintable caulk you can find. Paint two coats with masonry paint.
Popcorn ceiling is hard to fix and make it look good. If it's bad you'd have to scrape it all off and start over or do something else with the ceiling.
Not sure about cinder block walls, I've fixed concrete before by making cracks slightly bigger with a chisel and then applying a slightly elastic filler. Not sure if that works well with cinder blocks though.