You hit the nail on the head Inky. Putts do not take hits off of your ball, thus the reason I said what I said.
When I say barely miss a putt, what I do is imagine for instance that the cup is one cup left or right of the hole. I putt to make that and watch it roll. The other thing about this is, certain greens don't read correctly (as I'm sure you already know). This will give the user a better idea of how to play particular lies on the greens.
It may sound silly but it's worked for me. (not that I'm good by any means)
You can also pick certain "marks" on some greens, a mower mark or something similar.
I don't think you were rude at all by the way. No worries :)
Good luck!