I use thumb slugs in all of my equipment. It gives me a buffer between my thumb and the coverstock, and I prefer the quicker release of the urethane slug. Most thumb inserts are made of vinyl, and with the humidity in my area, this could lead to the thumb sticking in the insert. If I could find a urethane thumb insert that I liked, I might choose to go that direction, but so far I haven't found one out there yet.
As for hammering in a slug, my driller uses his drill press chuck to press the slug into the ball. He puts the slug on the edge of the hole, puts a push block between the drill press chuck and the slug, then he just cranks down on the drill press.......it really drives the slug in neatly and quickly. This is one of the neat features about the newer Jayhawk drill presses, as they can take this type of punishment without any problems, and it alleviates any need for hammering. Once everything is in position, it takes about 2 seconds to seat the slug into the thumbhole.
