Here is how I use yellow Frog Tape as well as Blue Dolphin Washi Tape. First of all, if you are going to use either tape over new drywall or a skim coat, the surfaces need to be properly sealed so that sanding dust does not weaken the bond on the primer or top coat of paint. (If you are not sure about getting the surface dust free, you can prime/seal with a product like Gardz. That way the dust becomes a permanent part of the wall. On a repaint all surfaces must still be clean and dust free.Got some frog tape as suggested by another member here. I need to put 2 coats on but the instructions say to pull the tape off immediately while the paint is still wet. Does that mean, I have to pull the tape after the first coat, let the coat dry and mask it again before the second coat? Or, can I leave the masking tape on while I wait for the first coat to dry for 2 or 3 hours and pull it after I second coat it?
If you are going to tape off crown, doorjambs or baseboards first make sure you have a good coat of trim paint on that extends beyond onto the ceiling or wall about a 1/16" - 1/8".
Next put the tape on following the edge of the trim you are painting against. With trim that is 90 degrees from the wall or ceiling you can use the roll of tape flat against the wall or ceiling to "automatically" get the tape where you want it to be.
Using a thin spackle knife or some such tool, press down on the edge of the tape against which you are cutting in.
With a very thin-tipped paint brush (I like to white angled brushes sold at Hobby Lobby and Michaels craft stores) brush a very thin layer of the same paint that is currently underneath the frog or washi tape. Paint directly against the edge of the tape where you are cutting in. Let this dry for about 15 - 30 minutes. This thin layer of paint will seal the edge of the tape so that the paint you are going to cut in with will not be able to seep under the tape.
Paint the wall or ceiling with a small brush that will cover well and not leave to heavy brush strokes. Immediately pull the tape off at a 45 degree angle moving forward in the direction the tape is running.
Doing color changes on inside and outside wall corners is pretty much the same thing: 1) make sure the paint on the wall you are putting the tape onto extends a fraction of an inch onto the adjacent wall (let this paint dry thoroughly, overnight if possible). 2) paint a thin line into the corner of the same paint that is under the tape and let dry thoroughly (you might put a fan on it). 3) brush a coat of paint onto the wall in that wall's color. 4) immediately pull the tape off at a 45 angle and away from the other wall.
Practice makes perfect.