I wondered about the silver paint too. The red on my Santa Fe F3 Warbonnet engines looks like it just came out of the paint shop, but the silver paint has quite a few scuff marks. There are no scuff marks in the red paint.
I was wondering how to clean silver painted bodies as well. I thought I remembered reading that Testors Silver (1146?) is a close match to Lionel’s silver. Has anyone had any experience with cleaning and touching up silver paint?
If the engine is a basket case, a repaint might be in order. However, I suspect a loco with a few scuff marks in the paint will look better then a loco with touched up paint.