thanks chris...i think i will adpat your idea and use a thin wooden dowel type device....so as to not scratch anything...

Hook up the diff. tester in #1 cylinder without the air on and as you turn it over and it is on the compression cycle, the gage will start to increase. Move the pulley mark to tdc. Do the same thing on the next cylinder you want to check. You can do the right side then the left side, no need to do it in firing order. Don't stick anything in the cylinder.