I have two methods. For my RC I 3d printed a rudimentary dial indicator that magnified small movements. www.thingiverse.com/thing:4607036
I just had to also print a part that could hold in the focuser.

The other method uses my planetary camera and a star or artificial star. Start looping frames and the HFR graph will begin to populate with samples. It's then a matter of finding a backlash setting that returns to the same HFR after In-Out moves reliably.