proper use of arc protractor ?

I would just add a couple suggestions to Mark's very good post above. I presume your Mint is designed for your specific arm (and cartridge, if the headshell has holes but not slots like SME arms).

First, you must make sure that the turntable platter does not rotate (or move at all) while using the Mint. I wedge a pencil eraser in between my platter and subplatter to prevent this movement. Don't forget to remove the "brake" before you try to spin LPs again.

Second, make sure you have a very good light while working. This can help you see and prevent eye-strain.

Make sure the anti-skate is set to zero. Also, the VTA will change overhang slightly, so make sure your VTA is very close to where it will end up if you frequently adjust this for different LPs.

Relax and be patient. It takes time but the results are well worth it.

Yes, Audioblazer. I think you observation is correct and I don't know how to get around this. My point was just that the VTA does change the overhang, so I set VTA roughly where it will end up (because I don't change VTA for each LP with my SME V arm) before I try to align the cartridge with the Mint.

I would think that Kip took this into account when he designed his glass protractor. I think it is close to the thickness of a 180g LP, but I haven't actually compared the protractor to various LP thicknesses.