There are many schools of thought on this subject. Prefferably, I like to start the snap like full scale. Break the Elevator Aggressivly, induce auto-otation with full aileron and about half rudder. As the stopping point nears, reduce rudder and finish with about half power and aileron. After the initial break of the elevator, you shouldn't need much elevator to continue the snap. The more elevator you have, the faster the airplane will slow down especially on the up lines, making them much more difficult to stop precisely. Remember speed is your friend in stopping a snap, but the rate at which you stop is dependent on servo power. Hope this helps,
Mark Leseberg Jr.