The boneyard idea sounds good. I'll give it a try.
In the meantime I've discovered a useful feature of my wheel. I have the three brushed-stainless spoked wheel. The FSM calls it a 'sport' wheel. I removed my wheel and carefully cut away the stiches along the wheel inside diameter. At first I thought the wheel was made by a complete molding and that the stiches were fake. They aren't, and when cut away the outer covering can be pulled off. Mostly this comes completely off, but in the locations where my hands were receiving the black gunk the padding has turned from foam to tar and the tar residue remained on the wheel. A little rubbing with MEK removed this, and other adhesive residue.
The removal exposed the molded steering wheel. It's really nice! The brushed-stainless spokes are nice all the way out, not just where they can be seen. The wheel is a soft white plastic. It has a kind of no-slip surface that I can foresee will become dirty with use. But a little MEK from time to time will fix it. I didn't try, but I bet it could be painted with a flexible plastic paint. I'm driving around with it now. Better than the black gunk.
The down side is that the wheel isn't as padded. This is done to soften the blow your head receives in a crash. So watchout!
In any event I'd recommend stripping the wheel as I describe above prior to recovering. If the recover people don't do this step the resulting grip diameter would be too large for my liking.