Just in case no one has seen this. The following web page has a good explanation of drift alignment and a drift alignment simulator.
The drift alignment simulator may not be the best thing since sliced bread, but close if you do drift alignment.
Click on the drift simulator on the left side of the page.
Just practice on the simulator and by the time you get out in the field drift alignment should be like second nature. However if you're like me you still might want to tape direction to your mount.