LTMW is doing a group buy on the walnut shell blasting - $350, plus a car rental for the day is included. http://www.e90post.com/forums/showthread.php?t=732369
And since it is LTMW you know that they are going to do it right! I know you are down in San Diego, but I'm making the 4 hr trip down from Lemoore to get this done since I know that it is worth the drive. The last page of the thread only shows one spot left open, but apparently a couple of guys have fallen out so there should be room to get in there.