Knowing how to do it is the easy part, but a couple of the video walkthroughs are more cautious and/or complicated than it needs to be. (Level 16 and 18 you can pretty much blow through parts of it instead of circling around waiting.) I've already racked up ~950 deaths. About half of that from level 18 alone. and I'm still stuck on level 18.
Just wait on one side for the enemies to come from that side. Slip through and grab the coins. Turn back before or when the enemies turn back and press the square up against the bottom wall or the square won't make it. Repeat on the other side.
