What about some sort of industrial grade cleanser ?
When my dad worked at the Enron Power Plant he brought home loads of hte stuff, and it cleaned alsorts. Its got a sandy type texture to it, it would clean vandal grase off your hands like it was standard dirt (i know, after abit of climbing on the local school my hands were abit black with vandal grase. Nothing brought it off at all, tried everything, and i mean everything. Then my dad got this ...this stuff out and it just brought it off with such ease.