Adun,
I echo what the other two guys said. I put mine in the dishwasher regularly and I add some liquid Dawn in the soap dispenser and run a short cycle. The Dawn will help attract the oil.
The other thing I found that works pretty good but you have to be very careful is a black garbage bag and a sunny day. Check the ball frequently but the sun and the heat from the bag will pull out the oil. I have done this but you have to be careful you dont let it sit too long because that bag gets hot inside. I have also put the oil-dry stuff you can buy at Auto Zone in with it and it works almost like the Hook Again stuff in that it soaks up oil in the bag just like off of your garage floor. After I take the ball out I clean it with a mixture of simple green cleaner and rubbing alcohol to get the oil dry residue of the ball and that works as well at least it has for me. Good Luck
HM, Level I USBC Coach