I've been using dish soap, but it doesn't do much. I used Mayhems Ultra Clear soft tubing, I wonder if that's the problem. I thought plasticizer would be more soft and rubbery though. This stuff is hard. I'm having to scrape some of it off with my fingernails or metal tweezers, because the toothbrush just isn't cutting it. It's also caked down between the fins of the GPU block, making it really difficult to remove.
Looks good, I'll have to get some.