I've found the best thing for getting the undercoating off is a heat gun. I bought one at Harbor Freight for like $10 heat the undercoat up and it comes right off with a putty knife. It is messy but much better than a wire wheel (mucco messy)and a torch, gas is expensive man! Seriously it works great! You can then wire wheel the remaining crap in between, do it you'll see what I mean. Then if ya want you can blast. Let me know how it works out!