Decided to post this after reading comments about pledge...
I am supremely unconfident about weathering cars and engines. Is there a way to apply overcoat to original finish that might allow for removal of later weathering if one decides that the weathering did not turn out as expected? A finish where acrylic colors might later be removed, for example?
(I have noted that there is a GN 4-8-4 with very heavy weathering that has sat at ebay for many months, I think the reason being that the finish is not something that anyone else would want sitting on their layout.)