I think it's time to paint my ceilings. Only problem is, I'm not sure how to paint over what I believe is plastered ceilings. It's got the bumps all over it. Is that called a plastered ceiling? I've heard you have to water down the paint and I'm not sure what's the best way. What is the anatomy of this ceiling? Is it drywall that's skim coated and then plastered? If I wanted to have smooth ceilings can I do it rather easily or will it be difficult? Any advice/recommendation is appreciated!