Well its kindof difficult to describe with text but ill try. Ok you know theres a moulded ledge on the side of the trigger. Normally, you rest your finger on that ledge and pull the upper forward with your off hand to fire... now, instead of doing that, pull forward on the upper and keep light pressure holding it forward. Now imagine that ledge is your trigger. Using your trigger finger, reach across the actual trigger and press the ledge when you want to fire. You want to keep your trigger finger kind of stiff because you want it to trip the actual trigger as youre pressing towards the ledge.
By doing it this way, the upper is already being pulled forward. That means your sights are on the target and stay there (until recoil takes over) instead of being thrown off target immediately as the upper is pulled forward to fire. No more of that.
Second benefit is fire rate control. Letting off the trigger to stop firing is a move most shooters will do subconsciously without even thinking about it. It is a natural reaction, and fast. Once you get the hang of the amount of pressure required to hold the upper forward, 2 shot, 3 shot, 4 shot, and etc bursts are easy to control. Doing it the other way, we found that full mag dumps were easy but controlled bursts were not. By the time your brain tells your arm to let off pressure after it was just holding pressure, it seems that the mag is already empty. (For us at least)
The plus of having your sights start out on target instead of being yanked off, plus the added burst control equal MUCH more accuracy. Its extremely difficult to keep 30 rounds on target while doing a mag dump and starting off target in the first place.
If you notice that doing it my way is only giving you 2 and 3 shot bursts and wont go longer when you want to, its because youre using too much forward pressure on the upper. It really doesnt take much.
Be warned: youre gonna wish you brought more ammo!