I have a friend who has split two balls right down the middle by putting them in his oven. I know, he didn't learn the first time.
The Revivor that my pro shop uses blows warm air as it rotates the ball. This is a very controlled environment. Most of my equipment is pretty saturated after 60 games, and I wipe if off every shot and clean it before I leave the bowling center. If you're not this fanatical about surface maintenance you'll be lucky to get 40 - 50 games before you notice a real drop off in performance.
I've tried a hairdryer, and it's safe, but you can sit there for hours trying to evenly extract oil from a ball and it's hard on the wife's hairdryer, which, in turn, tends to be difficult on the relationship.
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Laneman