Tony pretty much hit it spot on. I have been using wd-40 and light compressed air for years. The wd40 breaks down the diff oil so that a light blast of air will draw it out of the diff cups. Another tip if you are really anal, Pt racing told me that using 100wt shock oil will work as good as wd40 and at the same time it will keep the mixture all silicone. Some say that wd40 can attack o-rings and plastic. I have yet to experience this though.