Hey There!
I would like to begin by saying I have the hugest respect for doing things the simplest way when it comes to almost everything, slot cars inclusive. I have balanced many an armature using two razor blades with great results. Recently, however, I acquired a little gadget that I could not resist sharing. It is older than my rivet chassis t-jets, so I would not consider it "high tech" by any means. Let's just call it refined. It's a called a watch maker's poising tool.

I think you can see how it works from the picture. It has a built in bubble level, adjustable jaws and leveling feet. The surface that the armature shaft rides on is polished ruby. If you keep an eye out on ebay, you can pick one up pretty inexpensively. I got this one for $17 including shipping. This is by no means the end all that be all, but I love mine.
Later, Serge

Always drink upstream from the herd. -Will Rogers
Yes, but nothing is better than the ultra-famous DANO-TRUER!
danvanman