After you scrape the popcorn, do you have to texture the ceiling or can you just paint?
I had great results re-texturing lightly just using a high-quality 1/2" nap roller and slightly thinned down joint compound.
I initially used an 'oval texture brush' after rolling the compound on (slap method), but ultimately chose the
more-subdued texture made with just the roller alone!
However, the highest recommendation I can make is to use the GLIDDEN 'PINK TO WHITE' CEILING PAINT ;
don't cheap-out and use just any flat-white; the final finish of the Glidden is just amazing! (very soft seamless look).
Removal (of the popcorn) depends on if it has ever been painted, and with what; mine came off very easily with just water sprayer & 10 min wait.
Very messy tho. Used both a popcorn-scraper -
http://www.homedepot.com/p/Homax-Ceiling...ceiling+scraper AND just a 12" drywall scraper with a sodacase-cardboard-flat to catch the 'droppings' (he latter was much faster).
The scraper was indispensable, tho, on the 16' ceilings section (along with a 12' aluminum telescoping handle)!
You really do have to get every bit of the 'powdery' popcorn crap off or the joint compound won't want to adhere to the drywall, making texturing difficult.
I DID find that PRIMERING with plain original KILZ (OIL based only) prior to re-texturing made things go much smoother (it penetrates any remaining powdery stuff and eliminates any adhesion issues). It HAS to be the oil-based; the latex kiltz won't penetrate & bond like the oil stuff does.