I've always been a paint-by-hand guy. But, it was a bit slow (ok really slow) since I was kinda meticulous (ok really meticulous). So when my son-in-law, Chad, wanted to use the blue 'trim-tape' to mark straight lines between the walls & ceiling and around doors & windows, I was curious but suspicious.
Don't you still have to take time to put the tape up straight? Yeah, but it's still faster and the line's straighter. Once the tape's up the cutting-in goes real fast.
This was a little out of my comfort zone. I've always done it slowly by hand, with that marvelous feeling of satisfaction that comes from seeing a razor sharp dividing line between wall and ceiling and knowing I did that. As I painted using the tape, I had to get used to not doing it on my own. I realized I should go faster, and relax; I still had to do the same work, but the straight line was the tape's job.
Putting the tape up straight and pulling it down took some skill and time, but overall it was quicker. And the line? Gee, it's better than I could've done by hand. And faster. And easier. But the tape gets all the credit and I get none! Since then, six more rooms, all taped. I did the math; it wasn't worth it.
Trust the tape.