UPDATE from November 25, 2017-- I dragged out another #227 that I had purchased in 2005 on eBay. It is a good runner, but had been restored and was until now missing its cab # and tender lettering. I had bought a pair of stamp pads from eBay probably from around the same time specifically for this locomotive and tender. Unfortunately, most of the silver paint (purchased from the seller of the stamp pads) had dried up over the years. As a result, my friend and I used what was readily available in his basement, which was Testors silver paint.
BEFORE: The paint on the locomotive and tender (again, both were restored prior to my purchasing them) were in good shape. No sanding or other prepping were needed at all.
TESTING: My friend Bill and I used an empty tuna can painted black to test on along with a piece of cardboard which was also painted black. I thought the cardboard came out pretty nice (and I saved it), almost like something Andy Warhol might have come up with if he operated toy trains.
OUTCOME: This was my first attempt at using rubber stamps to restore numbers/lettering on one of my prewar steam switchers. I'm pretty happy with how it came out. However, it needed quite a bit of trial and error to get to the results.
Tom