I also equipped my 40cm Dob with setting circles.
See the pictures and find attached the PDFs.
I have a 47cm diameter circle inside the rocker box with an arrow pointing to the current value. Only with friction one can rotate the disk relative to the bottom of the box. The disk does not move when rotating the rocker box.
Calibration is rather simple: set the rocker box level (a wedge under 2 of the 3 pods until it is level in two directions using 2 bubble levels perpendicular to each other), point to a star of known azimuth and rotate the disk to that value. The altitude on the scale should match the calculated one. An extra check can be putting the scope vertical and checking with the bubble level and the altitude should show 90 degrees.
Now one can search objects within 1 degree accuracy. Most planetarium apps like Skysafari (Android / iOS), Starmap HD (iOS), Mobile Observatory Pro (Android) show live altazimuth coordinates of the selected object.
Works much better than the Orion Intelliscope XT-10i which I have sold now.
http://skysurfer.eu/dobson.php