I use a router much the same as you do with the sandpaper. I start out with 500 work up to the final grit I desire on the ball. It's not a fast system but I get the grit I desire, it takes very little of the original cover off. Just be careful of your pressure.
If you're looking for something fast, easy, IMO it's not there. It does take some time but the final work is worth the time spent. Anything worth doing is worth doing right, IMO.
Depending on the final grit desired, depends on when and what grit I start finishing the whole ball. Don't just do the plug area to final grit then finish the rest of the ball, you won't be consistent, that way.
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az guy aka: R & L Bowlers Pro
rlbowlerspro@cox.net