This has been covered extensively in the 700R4 build threads. But here is a quick recap.
Pushing throught the brakes with a manual tranny is easier due to the direct connection between the flywheel and tranny via the clutch. Pushing through with an auto tranny is more rare, due to the fluid slip rate in the in the torque converter, hence the reason you can stop an auto tranny without a clutch. It does happen, but the compensation is knowing your rig and when its going to happen. Mine does it on very steep downgrades or going down ledges. I have gotten very quick at slapping my B&M megashifter into nuetral when needed.