Just in case some here didn't know this; White tape goes to the front (opposite the knuckle). Black tape to the rear (towards the knuckle). The tape ends are flat at one end and rounded at the other. The rounded end faces up. Looking at the tape this would seems to be reversed, like the rounded end would go down, like the shape of the thumb. Not the case though. It's rounded to help prevent peeling and rolling. The black tape has a slicker surface which helps the thumb release. The white tape has a grittier surface.
For most people, you want a pretty snug fit. This helps to keep from gripping with the thumb. I have a problem with this. The shur cushion helped with this. They only lasted me two weeks but after I was able to put in tape, get a snug fit and still get my thumb out without thinking about it.