Taken from a Hammer Forum..
Ball Prep
The first thing you will want to do is prep the ball for the bath. This is optional but some people report better results with prepping the ball first. Take 500 grit abralon, sandpaper, or a green scothbrite pad and dull the surface of the ball. Some say that this opens the pores of the ball and will help extract more oil from the ball.
Some people prefer to tape over the finger, thumb, and x-holes with electrical tape. Personally, I have tried taping the holes, but I have two issues with doing so. One, water got through the taped hole anyways. Two, the tape leaves a residue that you have to clean off afterwards. I have done numerous ball baths without taping the holes and have had no issues. This is also a good time to replace worn inserts. If your inserts are worn out, you can remove them using a pocket knife or you can get a grip puller. Scrape off any dried glue or pieces of the insert from the finger holes.
Extracting Oil
Now that the ball is prepped, it's time to get the oil out of the ball. Get a five gallon bucket. Put the ball at the bottom of the bucket. Fill the bucket with hot water from the water faucet until it covers the ball. You can also add in some liquid detergent like "Dawn" or "Palmolive" while the bucket is filling up. I have heard of people using "Simple Green" or even adding in a little bit of ball cleaner to the bucket.
Let the ball sit in the bucket for about 15-20 minutes. By that time you should see oil floating at the top of the bucket. Dump out the water and pull out the ball. You will notice that the ball will be very oily. Wipe off the oil from the surface of the ball. You can repeat the process until you no longer have oil coming out of the ball.
Drying
Wipe off any water on the outside of the ball and try your best to get the water out of the finger, thumb, and/or x-holes. Let the ball sit overnight with the finger and thumb holes facing down.
Finishing
Once your ball is dry you can reglue in new inserts if you removed them before the bath (I just use a bit of loctite super glue about halfway down the hole on the left and right sides of the inserts). You can now change the surface of the ball and/or polish it. Your ball should re-gain some of the hook it once had.
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Sean from Chicago
KILLWHITNEYDEAD
Viva La Marijuana!