This is very easy to do with a regular mil scope if the reticle is well done. You could easily do it with very little practice. Figure out what is 100 yards and divide by 10. A lot of cartridges 1 mil=100 yards. Those are easy. Flat cartridges are more like 0.7 or 0.8 mil= 100 yards, so a better way is to figure out x yards=1 mil and visualize the fraction while you shoot. The THLR reticle does this very well visually. If you shoot enough it is very easy. Being fast is about making shooting simple, yet precise enough to hit the target. It does not require you to be exact unless the target is very small or very far away.I see the math and the application of the shoot long and short, but without quite a bit of practice I doubt I would pull it off in a real situation.