Can't get a grip!

Cut the fingers out of an old set of rubber gloves, then cut them to fit from your knuckle on your thumb to the base of your thumb. Or I buy rubber finger cots, three boxes at a time and cut them the same way.
Some fellows slip a piece of surgical tubing over the reel foot long enough to get a grip on the spool, gets in my way fishing.

Another method is to use some 1/2" x 4" butyl strap (bicycle inner tube) under the reel foot. If using a screw winch fitting you need to make a small cut accross the strip.

Led.

RobC,
This is a little different from what the other gents are offering but this may help also. Instead of grabbing the rod and then putting your thumb on the reel, first put your thumb over the reel in a position which is comfortable for you and will alow you to control the spool. Then without moving your thumb, place your fingers around the rod grip. It really doesn't require a gorrila grip to control the rod. Hope that was what you were looking for
Tight lines and popped riggers