Hi first post so excuse any daft questions please. I have removed the rear subframe on my car to try to repair some rust above and behind it and issues with rusty reluctor rings and ABS warning lights. Bit of a pig to remove its a Mercedes R170 SLK which I've had since new and thought I took good care of it until the MOT guy spotted a hole where the floor meets the rear bulkhead and promptly failed it. Anyway subframe out stripped down and electrolytic bath later and its now rust free. Gonna give it some EM121 then some paint. Question is I cant find a media blaster within 30 miles exept a local firm that wants £200. I've been sanding grinding and scraping it myself so how far do I need to prep? there's still a little factory coating on but it's not going anywere fast. I'm gonna give it a final 120 grit sanding does this sound ok? I can post a photo if that helps