I used a Duro brand slow cure epoxy done in slow steps to fill all the cracks. Once it was completely filled I found that with age it was twisted and the edges didn't line up. I used 100 grit to get it all round again and refilled any imperfections again. once it was all round and completely cured it was finish sanded to 400 grit. At this point I put it in the freezer, and left it there for a few days. I took it out and put it in the oven on a warm of around 200 degrees. I did this with a different filler and it wasn't pretty. Ok the fill held the temperature extremes but all the resanding put the coloration off and took out the wood grain look in several areas.
I blended a sand and engine black Poly S paint made by Floquil to match the base coloring. I used this type of paint for it's adhesion and penetration into plastics, as well as it's compatibility with other paints and finishes.
At this point it's been sanded smooth and is just looking like a light brown steering wheel and hardly resembles stock.
I used the coursest sandpaper I could get and carefully redid the wood grain on it. Then rubbed in a Benjamin Moore hasbrouck brown. It's a water base but compatible with the Poly S after it is dry. To resimulate the wood grain it was important to use a slow dry water based piant that could be rubbed in without effecting any base coloring.
I finished it off in a full gloss krylon with a good UV rating. lightly sanding between layers.
So to fill was 7 or 8 steps, recoloring 4 more and temperate testing was 3 so far. Each step taking at least 48 hours in between.
It was cheap but not easy. BTW the pic is of it in mid cure of the first finish layer. It's not even for my car so go figure.