Rotary Tool Runout and facing operations?

Anyone worked out good workflow for testing whether their stock is actually in and running true in the jaws of the rotary tool? I get that most people won’t care that much, but I’ll be doing some pieces where “not much” is machined off, and if the stock isn’t fairly accurately true, it won’t come out correctly.
Similarly (and once it’s running true), any developed a good operation for facing the stock?

Runout gauge seems obvious choice.

After making sure my stock is fully seated in the chuck, I’ll usually quickly make a cylinder STL the size of the smallest diameter I measured across it. (I’ve used 50mm dowel and it’s never exactly round). I’ll load that into Luban as a surfacing operation first, then remeasure afterwards and use that for my actual carve.