Back in the 80s when I shot 22LR competitively I was fortunate to have a good mentor and friend. Offhand is naturally the hardest position to master. This man told me that you will never hold a rifle absolutely dead still. The trick, after developing much muscle control, is to get the rifle moving in circles. The more you practice the tighter this circle becomes to the point where, although it is still moving, it is almost imperceptible. Then you squeeze the trigger.
It almost seems magical that the bullet finds the center. I never shot a 100 10X offhand but shot a few 100 8X targets.
We had a gentleman on our sister team (our club had 2 teams) with the same initials as me who was a multi national champion who would shoot all 4 positions offhand and would usually beat everyone! Of course he was pretty young at the time.