If you can find a product called Opti-Kleen , it is super.Especially if used straight. I use it at work.
I had a big glob of thick copper anti seize freshly stuck to a steel painted bulkhead, 6 feet above an overhead deck.
I sprayed it on straight (no dilution with water) and the glob slid down in a clean trail. It's ABSOLUTELY non toxic and is used to clean fish hatchery tanks and is food grade. No residue if properly diluted.
Next up, and a new addition to Home Depot on the West Coat is Krud-Kutter. A less pricey version of OptiKleen. I have used 3 gallons recently over 3 months. It tears through grease and slop that is 10X worse than any work truck or old automobile will present. Just perfect when used non diluted and does a fabulous job when diluted on less bothersome messes and stains.NON TOXIC.
I enter very confined spaces in an Industrial Marine environment and the Purple Power,Zep, and other such rot gut is NO BUENO for my skin and it makes me ill with a short exposure.
Also, I regularly use my 2 favorites here to obliterate very dark soot diesel stains from bright white painted bulkheads. It rarely disturbs the paint, and the rest of the offerings eat the gloss right off of our Interthane catalyzed epoxy paints.
(Toxic in its own right).
If you tried my 2 straight, with a course scrub brush, you would be shocked at the results.
Just my .35 worth !
Good Luck !
Shawn