Twenty rep breathing squats are one of the most challenging exercises you can do. I was wondering why not follow DC's entire rest/pause program rather than just the squat routine? It is very simple to follow and the gains are easy to track. I have started to switch up the rest/pause with a GVT routine and I like what I see so far.
As far as the 20 rep squats go, make sure it is a weight that you can handle for the first time and then adjust your poundages from there. Good luck and it is never a bad idea to have a trash can close by.