Bend It Once, Bend It Right

To get the 90* with hydraulic benders in the right place I use this method worked out by a tech I first worked with:

Mark where the outside of the bend lies.
Go up a pipe size to what you're using and in from the bend and mark pipe.
Place centre of shoe of benders on the second mark and away you go. One right angle that lines up.

Seems a bit ad hoc but gave good results for smaller pipe. Not so sure about 3/4" and 7/8 though.

What method do the learned benders out there use?

Many thanks,
Andy.