NEVER use oven cleaner on lexan - fastest way to turn it into a pile of broken pieces. Brake fluid again will attack the lexan, it goes cloudy because the brake fluid is attacking the lexan and makes it brittle. Okay for something you aren't going to run, but if you race it the first impact it will split easily.
Nitro fuel is the best as it doesn't harm the lexan. Get as high a nitro content as you can, 30% works best.
I've recently been experimenting with
De-Solv-It Graffiti Remover as it does a good job of removing paint, even fuelproof ones. it seems okay so far on bodies but I haven't had chance to see if there are any problems over time.
If the body is available new it's a lot easier just to buy a new one.