DIY white wall buffer/cutter jig or machine?

[Rust-O-Matic]

I'm not sure where to post this, but here goes:

I'm looking to grind another set of white letter tires into white walls for my '66 C20, and am looking for a more "precision" method of doing it than the last set I did. I used a 5" rotary sander with 80 grit discs for those, and just free-handed it around the unmounted tires. It turned out surprisingly well, but it was difficult to keep things even and uniform.

I would love to have one of the old machines meant specifically for this purpose, but they are few and far between and ungodly expensive if you can find one. So I've been thinking about building some kind of jig to hold a grinder with a tire buffing wheel, and some kind of apparatus to spin the tire, which would be mounted on the rim, installed on the vehicle. Basically a poor man's version of the Cosmo G3000 I saw in another thread.

I have read through countless links and threads to try to get ideas, but I have yet to see anything homemade like what I'm describing. Does anybody have any ideas and/or pictures they can share?