I consulted a biochemist friend, and he suggested a good lab detergent. Fisher Scientific has a lab detergent especially formulated for plastics, VersaClean.
With my VPI, I used a mixture in the range suggested, plus alcohol to 10%. Since there are a hundred ways to denature alcohol, I used a pure Vodka - there is only one way to make pure Vodka - with ethanol and a charcoal filter. That, plus a distilled water/Vodka rinse served me well, until -
I tried ultrasonic cleaning. I use an Elmasonic from Germany, sourced from, you guessed it, Fisher Scientific. Now I use VersaClean and distilled water, no alcohol. The results are dramatically superior to the VPI - though at a significantly greater capital cost.