It all comes down to personal preference Manny ... but in older tinplate items of value , cleaning should be done minimally and in such ways that you don't adversely affect the original finish .. Of course that all comes with the proviso of ...are you buying for your own enjoyment? , or collecting hoping to make a profit later on ?... Each path will take you in seperate directions regarding cleaning , or god forbid ( lol ) restoring 
Something is only ever original once and if you personally love shiny shiny and plan to reduce the value of what you have , then by all means repaint or "restore" ... of course thisis all relative to the value of a piece .
No one is gonna go apeshyte if you clean and steel wool a Marx caboose , but do that to a 1910 Georges Carette loco will be a different story lol ( as you flush $100 bills down the toilet with each wipe of a silicone waxed rag lol )
Once you buy something , its yours to do with as you please , but yeah the same Gun example DOES apply to the older rarer stuff ...
