those that have schooled in the bullseye game have an easier time going to two handed shooting than combat shooters trying to shoot bullseye.
I'm taking my buddy who is an incredible shot and firearms instructor for the local sheriffs deptartment to my old bullseye club where they are having a 900 NRA style bullseyes match. It should be interesting!
As to rapid fire, try international rapid fire pistol matches. 25 meters, one handed starting at 45 degrees down to bench, gun in hand, 5 SECONDS, 5 SHOTS ON 5 DIFFERENT TARGETS!
For rapid fire or double taps, the trigger should be a faster version of condensed slow fire surprise shot. The main difference is that in real slow fire, ala sniper trigger work, the squeeze might be held steady as the sights wander off the target, and then the squeeze starts again when the sights come back on. Sight alignment is,of course, more critical than sight picture.
But in rapid fire, combat or bullseys, the trigger is squeezed constantly and the main focus is staying within the black, target zone or COM. But in both types, the shot should be surprise and you hold through each shot, letting the recoil trigger your recovery. Reset happens AFTER the gun is in recoil and your trigger squeeze or pull happens BEFORE coming back into sight alignment.
People tend to jerk the trigger because they are "snatching" it when they see the proper sight picture (not enough focus on sight alignment) or they are losing focus THROUGH the shot and are already trying to think about the next shot.
1. Hold your gun on the target, finger off the trigger. Slip your trigger finger onto the trigger, Then in a determined effort, pull your trigger constantly through without thinking about when it will go off. Sort of like a constant total surprise trigger break. Just focus on holding within the black and let the gun go off on it's own. By breaking down the sequences of the rapid fire shots, down to one fast shot at a time, you will be able to pick up your speed with subsequent shots. Try too much at one time and you will be embedding bad habits.
2. After a good rapid trigger break, just bring the gun down into sight alignmen for the second shot....without taking it.
It's sort of like paired sight alignment shots without taking the second shot. You come back down from recoil, get your finger set up for the second shot but do not take it. The reason for this exercise is that it eliminates the focus on the SECOND shot and lets you work on all the elements up to that point.
I found this out when teaching martial arts. If you teach someone how to block and punch, they are too focused on the 2nd act, the punch, to focus enough on learning the correct block. But if you teach them how to properly block, and SETUP for the punch, they can learn each element correctly, and the punch, (like the 2nd shot), comes more fluidly and natural.
Sorry for the long discourse!