Soap and water didnt do much if anything, tried that using full strength Dawn and a rag.
IPA - helps but doesnt get rid of all of it. I got the heavy stuff off with it.
What is working best that I have on hand - Tom's Natural Toothpaste... It has Baking Soda and Bamboo Powder as polishing agents in it. Damp rag, a small amount of that and lots of scrubbing are getting the finer lines off. Still not perfect so I plan on trying some other items. At least this weekend is supposed to be rainy so I can just hang out and scrub key caps!
All pens are going WAY out of reach from now on! Of course has has climbed on top of my desk in the past as have my other two boys at his age.