I took them out one by one and gave them a quick scrub under running water. It took me about 15-20 minutes to clean the lot of them with an old toothbrush. I must say I was very impressed and even without the toothbrush, you could see the layers of paint just washing away. Apparently it is a good idea to give them a good scrub under water though as any residue simple green will cause problems when it comes time to undercoat them again.
Once I was done, I laid them out on a piece of paper towel to finish drying. There's now an Eldar Jetbike resting in the ice cream container for tomorrow night.