I don't know how much it is, but last night on the tube, they advertised Frog Tape. I've never used it, but the commercial shows that when you paint, the moisture from th epaint activates something in the tape that makes a seal. Then when you pull it off, it leaves a crisp line. Again, I don't know personally.
A buddy bought some vinyl tape and did his garage and it turned out real nice. His walls have some texture to them. After he put the vinyl tape on he took a small roller and kept rolling the tape down. It filled in the voids from the textured wall by doing that. I have a site bookmarked but it's on my other 'puter.