Ken
Some day when you have an hour or two to kill check out this site:
http://www.consolidatedstripping.com/pages/1/index.htm
The owner, Don, appears to have a PhD in blasting. Looks like his shop has 5 or 6 cabinets and an oven or two -- big enough to cook and blast an entire car frame. He'll let guys rent his stuff on site. The first time I found this site I think I was looking for 3 hours. He talks about 4 or 5 grades of blasting, media, and stratia, etc.
I have never talked to Don but have corresponded with him on e-mail. I'll bet that if you can't figure out the media to use for a particular job, he'll help ya out on the phone; he came across as that sort of guy.
I have saved a lengthy e-mail response from him in which he discusses compressors. I can post it here if you are intersted in that, too.
Craig