It's a little easier if you use a wide masking tape. Something that's designed to give clean edges under emulsion (frog tape does this but it's not wide). With a wide stiff masking tape it stays straighter. You need to be careful that the tape will not pull away the fresh emulsion you are creating the line against.
Pulling it off cleanly is a bit of a lottery. It does seem easier when the paint is quite fresh, maybe not quite fully dry and pull away from the line at about 45 degrees in both directions. Do it slowly. Some people prefer to roll it off (See "Better Call Saul" Season 3 for an example).
In the scenic industry I've seen guys do it by hand!
It's a little easier if you use a wide masking tape. Something that's designed to give clean edges under emulsion (frog tape does this but it's not wide). With a wide stiff masking tape it stays straighter. You need to be careful that the tape will not pull away the fresh emulsion you are creating the line against.
Pulling it off cleanly is a bit of a lottery. It does seem easier when the paint is quite fresh, maybe not quite fully dry and pull away from the line at about 45 degrees in both directions. Do it slowly. Some people prefer to roll it off (See "Better Call Saul" Season 3 for an example).
In the scenic industry I've seen guys do it by hand!