I wouldn't have a problem with a shop being honest about their ignorance, I've done business with more than a few shops that I only found out after the ****** job that they didn't have any idea what they were doing. There's really nothing complicated about this job, I'm sure they have plenty of experience doing similar work so once someone tells them what prep process to use I have to believe they would know exactly how to do it.

I'd PM Luna X, he was in the body shop business for a few decades so he might be able to give you the best advice.