Ronald,
If the radiator is chrome plated it's pretty easy. If the letters are recessed, take the color paint you want to use and dab it into the recesses. Don't worry about coloring outside the lines, we'll take care of that in a minute. When the paint is dry, take a wooden toothpick (plastic ones should work, I've always used the wooden ones) and gently scrape the dried paint away from the letters. You now have painted letters. If they are raised, take either a new #11 blade or a fine grit sanding stick and carefully remove the plating from the letters. After doing that, take your paint and paint them. Once the paint is dry, grab your trusty wooden toothpick and gently scrape the dried paint off. You may need to sharpen the tip to get into the nooks and crannies. Sorry I don't have pics, hope this helps. As to a magnifier, can't help you there as I don't use one.