The short answer is yes...get finger grips and a thumb slug. The advantages are with a thumb slug, it's easier to release your thumb at the bottom of the pendulum swing, which will allow you to hook your ball. Finger grips help with gripping the ball better during the swing and also with hooking the ball. Your strike ball should have finger grips and a thumb slug. Your spare ball should also have finger grips and perhaps a thumb slug, though, what I have gleaned from the board is that thumb slugs aren't really necessary for a spare ball since you are pretty much throwing the ball straight instead of hooking.
My spare ball [Columbia White Dot] does not have a thumb slug, but does have finger grips. However, I may have a thumb slug installed to be consistent with my entry-level ball [C300 Scout/R] which has both grips and slug.
Hope this helps...
Billy