Need some help with Brake issues

You just need some streight edges and a caliper or a good mechanics rule. If you get it close youl be ok.

Another way would be to adjust the rod a bit long, set the master in place, there should be a bit of force needed to make it sit flush. Then adjust the rod a half turn shorter and do it again. Repeat till you get to the point the master can be set in place without any force. you are probably at the correct spot.

You could test the clearance with some (in know i know) lipstick on the end, thin coat. Assemble with the nuts and then remove and see if any of the lipstick transfered from the end of the pushrod. If it did it might be too tight.