I came by a nice little trick from watching some youtube videos by a man who's youtube username is "hpiguys". He has been building models and making videos for 4 yrs at least. His video's seem almost professional compared to most others. For one thing he mounts the camera on a tripod or some other device that holds the camera rock steady! No motion sickness when watching his videos. This is something I have seen him do but never tried it myself until recently.
This is not so much for a radiator shell as it is for the radiator core when inside the engine compartment. He used a silver pencil as you can see in the photo.
DSCF0009 (4) by
Nathan Pitts, on Flickr
This is a silver pencil. Hard to find by itself but found, like I found this one, on ebay now and then. Sharpen to a dull point, not sharp. Lay down so the side of the color center is what is doing the marking, not the tip, on what you are trying to color and rub from side to side, repeatedly until you are happy with the result.
DSCF0013 (4) by
Nathan Pitts, on Flickr
1957 Ford car radiator saddle frame and radiator......BEFORE. Rustoleum satin black, not gloss.
DSCF0015 (3) by
Nathan Pitts, on Flickr
Same radiator AFTER the silver pencil treatment. You rub back and forth as long as you like. The more you rub the more it will color, but it is NEVER like any aluminum spray or god forbid Testor's silver, which I have used for a long time but is just too gaudy for something like this. The radiator core may have been silver like when new but did not stay that way long. I find this to be much more subtle and effective.....and pleasing to my eye. Best part? You can wash it off with warm water and do it over if you want.
Video!
https://www.youtube.com/watch?v=lu2Xd5rPobw&ab_channel=hpiguysWorkshopThis is Chris (hpiguys) doing a 67 Chev Impala rendition of the "Supernatural". Man is a good teacher and great eye for artistic stuff and does the most interesting things with cheap stuff you can get at the dollar store or Wally world. Some vids are kinda dry but I learn something in most of them. The silver pencil he uses a lot for lots of things.