I can never seem to get the cube OOB quickly and consistently. It always seems to into the next room and not OOB. What's the technique?

There are a few ways to get the cube OoB:

1. The easiest one is to just go farther away from the cube. When the cube is farther away from you its speed will get greater and if you're far enough the speed will be enough to go through walls. Also, if you look in the opposite direction, away from the cube, it will be faster.
2. Flicking it OoB. Try that by standing OoB on a legde while the cube is In Bounds. If you move your mouse up similar to how you go OoB, the cube will also go OoB.
3. Pausing: If you quickly pause and unpause the cube will likely go through the wall. You can also combine the 3 in some way, if you want. Hope, i was able to help :)