I've found the Simple Green "bath" works on some cars but not on others. If the body has a clear coat Simple Green doesn't work well. I soaked my Carrera Roadrunner Stock Car in Simple Green and it worked great. I soaked a Carrera Corvette with the American Eagle paint scheme and Simple Green didn't touch it as it had a good clear coat. I've used Simple Green in my ultra-sonic cleaner on some of my HO bodies that were repainted, and some Johnny Lightning bodies. In the ultra-sonic cleaner the bodies came out perfect.
I have used oven cleaner on bodies that have been painted to remove the bad paint jobs. If you use oven cleaner keep watch on the process! The stuff is nasty! Very bad odors and fumes! I didn't leave trhe oven cleaner on the body for more than 30 minutes. The key is testing and keeping an eye on the body some the oven cleaner doesn't damage it.
Brake fluid is another product you need to be careful with. If you soak a body in it you again need to keep an eye on it. If left in brake fluid too long the body will suffer damage!
As with ALL chemicals, when using them wear protective gear! That includes eye protection, the proper gloves, and a respirator if the chemical gives off fumes!
------------------Bill