He's right about the paint color. Sometimes the vinyl is so thin that the under-painting color will show through, especially if you painted white.
Dry method means that I measure and place my artwork, tape it down, then cut the backing and roll smooth onto the cab. I usually will cut the backing about 1/3 the way down from the top of the cabinet, then roll up, then roll down and finish the artwork off. Then cut excess. There is no budging, you need to place the art perfectly, because the whole idea is that the artwork will not slip at all with this method. Masking tape is your friend here!