If you scrape the thick layer of grunge off with a scraper or an old credit card and a tooth brush wire brush you will have the part close to done with less residual mess in no time. Then do what Jason suggested and melt the thin layer off quickly. Often times you will find paint codes or painted number / letter codes this way, too. Harsh chemical cleaners tend to wash these away before you ever get to see them.
I thought I would update this with the "after" results: This car had never been cleaned below the waistline. Grease and grime an inch thick - you get the picture. Both cleaners I mentioned* worked well. I scraped then I sprayed the cleaner, waited a bit, and used one of those copper round scouring pad (be careful, the cheap ones are copper plated plastic). After it souped up, I rinsed with water from another spay bottle. Repeat. One pad lasted quite a bit. I found that using a (hair) dryer minimized the flash rust. Total effort was minimal. It took the old paint off as well, leaving bare metal. Use a fan w/fresh air as the fumes are strong. I did not dilute the cleaner. *Purple Power - $7 for a gal. (Walmart) Super Clean - $ 10 per gal. (Walmart) I did not use the WD 40 stuff. This was done on a lift inside the garage. I used a bin with sheets of newspaper in it and put that under the section I was cleaning. The newspaper absorbed the run off, then I tossed the soiled paper and put in fresh paper.
Old thread I know... Scrape the initial crap off from accessible areas, then I used LA's Totally Awesome 100% straight. Let it soak on the grease, then pressure washed with a car wash high pressure wand. WEAR Protection! I used a full coverage TYVEK suit and face shield.
I used Purple Power for probably 20 years, bought a 5 gallon bucket every 6 weeks or so. Last year they changed the formula and it no longer cuts grease, as far as I can tell, it does nothing, just sits there. Now they came out with Super Purple Power, which is the old formula at twice the price. Rip-off-flation!!!! Typical corporate greed!
