As a pinstriper, I can say its just another method for palletting the brush. Most stripers pallet on an old magazine or out of a paper dixie cup. Some like to pallet between their fingers because they can feel the consistency of the paint better and get the edge of the brush nice and sharp. I don't like getting paint all over my fingers and can get the same results palletting on a magazine. It's really just what you're used to and what works for you. Btw, there is a difference between a dagger brush and a sword brush. Most stripers use a sword style brush in which the top of the brush and belly of the brush are different. A dagger brush is symmetrical, meaning it the top and bottom of the brush are the same.