I tried the walnut first and found it didn't work well. The pieces bounce off of the material and don't have the tooth I was looking for. When I switched to glass, it was smooth sailing.
What grit glass are you guys using? Turns out that the finest they have is 80 grit.
Which brings up another question... is it the grit or the hardness of the blasting medium that I should be most worried about? I can order in white aluminum oxide down to 220 grit.
Scott, Thanks for the offer. If I haven't found something that works before then I'll take you up on that. I have a lower A-arm that has a small section I tested today. It'd be interesting to see a comparison on the same material.
Rhino, check local Harbor Freight or Northern Tool, usually they have blasting media, although HF has ridiculous prices on media compared to the rest of their products,it might help you in a pinch.
I would try walnut shells or plastic, anything coarse will leave surface finish prone to get dirty quick and PITA to keep clean
__________________
Stefan B. Do what's right,not what's easy!