Putting in this three piece crown molding in my two front formal room. I've already installed baseboards, window casing, and trimmed out the entryways. I'm having a hard time figuring out the crown mold. I've never done this so its been a learning process for me. Normally I'd hire this out by I thought I would have some fun and do it myself this time. Save myself a couple thousand dollars too. Still bout 500 a room for material alone.

Ok. I'm going to try and describe exactly how the crown is going in and then ask my question. I have two pieces of plain colonial base board. I'm putting down one on the wall and the other on the ceiling then the third piece joins these two at an angle between. Looks like this.

I understand how to install the wall one. And I know how to install the ceiling one by nailing to the joists. My question is what are you nailing the ceiling one to on the wall that doesn't have joists crossing it? 

Also tips for making those corners tight and not needing so much caulk would be appreciated. How do you deal with walls that aren't square? Been driving me nuts. 

Seriously been driving me nuts.

Also, cutting returns with a coping saw sucks. If there is a better way to do this than with the compound mitre saw with the duel bevel, I'm all years. Are you using some sort of jig? How do you make it?