When drilling a ball for an interchangeable thumb sleeve (Grip-Loc), do you normally drill the thumb pitches into the ball?  Is this the best way, or what is recommended?

Correct, drill the pitches in the ball.

Not sure if any of these videos help or if you have already seen them, but Tom at Grip Loc sent me these links a while back.

And of the 3 . . I'd recommend the Vise IT system.  It's the most labor intensive, but I've seen the best results out of it.  Even with improvements, the Turbo system is still pretty fragile, and I really dislike the full sleeve insert into the ball.  The IT system in my opinion has the best anchoring and the smallest contact points. 

Me too, but I'd also recommend a vent hole in the slug.  It's very smooth, so it can create a vaccuum on your thumb if your fit is "too good."  It's not very hard to do, I think I made a video to that effect once . . easiest to just take a bevel knife, put the tip into the vent slit near the bottom of the slug (close to where the bottom of the thumbhole is) and work it back and forth until you've made it into the thumbhole.  Lets air into the bottom of the thumbhole by way of the vent slit that runs from top to bottom on the side of the slug and relieves any "sticking" that it feels like may be happening.  You could always do it with a power drill and a super small bit, but the bevel knife is the easiest, handiest way to do it.  I like it even though I don't drill many balls just because once you get a thumbhole "right," that's all she wrote. 

I'm glad you said that I was thinking about using the Vise It, again I like the feel of the slug texture over others I've tried.