I've done every method out there to remove the oil from bowling balls.
The best method is having your local pro throw it in a rejuvenator...but that costs money. I prefer free.
My personal favorite is the dishwasher. Just toss it in, don't use detergent, turn off the "dry" function, and run it through a normal cycle. Almost no labor and works like a charm.
Baking in the oven is not a good idea unless you have an oven with a "warm" feature that doesn't get above 120 degrees. (I've heard up to 140 degrees is okay, but I'm skepical...) However, it's labor intensive because you have to clean the oil off the ball periodically. Too much work for me.
Hot bath is okay, too. It is also labor intensive as you should periodically wash the oil off the ball while it's soaking.
Kitty litter works okay. I've found it works best if you put it in a box filled with kitty litter and then put the box into the trunk of your car on a sunny day. Kinda messy and also costs money...kitty litter ain't free.