I picked up a MP optimus prime, voyager Evac and voyager Ironhide last night. The figures are in great condition, except the house they were in had a cat, a dog and it was a smoker house. There is a layer of dust, dirt, ash on the figures. I ran my finger over some of the white parts on evac and luckily there is no yellowing, but my question is how do I get the layer of dirt and ash off? Just dip a rag in water that has dawn in it and gently scrub? I just don't want to remove any paint if possible. Thanks.