I finally got to try my idea and it works!!!
I used an old wood burner tool I inherited (just like an electric soldering iron) and after filing out a cracked area on my steering wheel (was about 3/16 of an inch when done), I simply melted in some small chunks of plastic from an old badly cracked Chevelle wheel I had.
There is a small learning curve but not bad. It melts at the slightest touch of the tool so things happen fast.
Once I melted enough in to fill the gap, it cools within seconds so I took a file to it and it shaped real nice. Quite easy to work with. I then took some fine sand paper and worked it further.
I had a few small low spots but not a problem, just melt in a little more plastic! I think a little high build primer or glaze would be fine for any surface imperfections as the crack itself is now welded together.
Now the real test will be does it hold up? I'm thinking it just might as it's the same material your using so it will expand/contract the same as it's surrounding material and also, the new material melted into the old really making it one piece.
Ok, you can start calling me a genious now.
I shouldn't be telling anyone this, I should start selling kits with the iron, plastic material, files and sand paper and get rich! LOL
Give it a try! I am working on a black wheel and using a scrap black wheel but I bet colored wheels would also work. In fact, given the right touch and grit paper, I bet you could shape and then work down to very very fine paper and buff out. That way no paint would be needed.
My wheel has too many cracks to do that method so I will paint it when done.
I'd love to offer pics but my camera sucks with close detail. Here's a shot showing the crack all filed out, ready for the new material. That crack cannot be found now! It's like it was never there.