The biggest "cheat" IMO about snaps is finishing the snap with ailerons only. They are much easier to stop precisely this way. Its a gamble though as if the judge actually sees that the last 45 degrees were not a snap but a roll, he has to deduct 4 points only for that.

The trick is to finish with ailerons but making sure it is not visible by keeping some rudder and/or elevator.

Apparently, Dick does not only know how an engine works, he also knows how to fly .

The one thing I would add is use the least amout of elevator and rudder possible for a good snap. Anything more will eat airspeed and exit heading. Lots of ailerons, a bit of elevator (low rate) and a bit of rudder (low rate).