I know you said that he cleaned it regularly...but you also said you did it for him in your shop. That means, I'm guessing, that it wasn't done RIGHT AFTER EVERY set he bowled, correct? Instead, he probably bowled, packed everything away, came back next week, cleaned it, bowled, etc...this is not the proper cleaning method encouraged, especially with the new coverstocks that need so much care and attention...
Maybe I'm wrong, though, and you did clean the ball for him after each set. I just doubt it from your description.
In terms of restoring hook, you could try the hot water bath first. Your chances of hurting the ball or doing anything are slim to none, especially when you take precautions like covering the holes (which is recommended, by the way, if you ever talk to some ball manufacturers). After that, Ebonite's Hook Again, the CPR, or the Rejuvenator all might help...but only, in my mind, for so long. You can't ever really get a ball back to OOB condition -- that's impossible, unless you plan on going to see Dr. Emmett L. Brown...
Regarding getting money for the ball, I don't know if I can entirely encourage selling a ball that you know is not worth $$$. It just doesn't seem right -- you'd be taking advantage of somebody else's ignorance.
Lastly -- and this is totally unrelated -- I thought of something when I read the title of your post. How cool would "Dead Shift" or "Night Shift" be for a ball name??! Who wouldn't like a zombie/S.K./dead-end (sorry for the pun) job reference on a bowling ball?
