I think you may have it back to front ?
The side that has the centre high spot should be rocked upward starting with the toe slightly raised to make contact at the heel .
The side where the centre is not flat on the stone should be rocked downward... or is that what you are doing ?
Personally I find these actions easier with one hand but I know not everybody does that.


Another thing is that the thumbnail test is not so different to to using the glass on the edge. A little more honing after the TNT is always needed before attempting to cut hair.