The concentric circles are done with an airbrush and some paper templates- you can see them in the background of one of the Thomas Models pics. You can get a special paper cutter that can cut circles of any diameter at your local craft/scrapbook store like Hobby Lobby that would be perfect for this. The radial lines can probably be taken care of with small pieces of tape.
I've only built the "Mirror, Mirror" version (2nd pilot style), so I haven't tried out the concentric circles yet. Soon though
Makes a lot of sense! Missed that pic with the weathering rings - thanks for pointing it out. This seems like the ideal model (read cheap) to try out this technique.
I don't remember where I read about it (maybe the idic page? I don't have a link) but the E model supposedly only had the rings after the "restoration" project, and not during filming.
It'd be easiest to do the concentric rings first, and then tape off the linear segments. Shouldn't take much time once you've got the angle and spread down... have fun!