50/50 mix of ATF and acetone, let the end soak in it. Will break all the rust up no problem.
Not sure which bushings you have but, I had talked to, Johnny Spiva at, Poly Bushing a while ago about splitting his poly bushings, he said that’s fine and wouldn’t be an issue. However, they’re incredibly hard and dense. Your not just going to slice through them with a razor blade. You have to boil the poly bushing and get it real soft, and have a real sharp, thin fillet knife that you may need to be whiling to heat up red hot to make a clean cut.
One of mine is cut, one of them is not. No issues either side. Just didn’t have the gas left in my tank to beat apart both sides.