Sao Paulo Pass is prob one of my favorite passes. I normally stand to pass, but I still love this pass. If you're not good at passing half guard you will slowly get better because you won't get the pass all the time, especially against someone with good guard retention. But if you do it right, you should be able to blow by them. There are two key things you need to do, and you will see in the videos I'll post below. One, is the arm you are using to underhook/non passing side cannot be defeated or you have to start over. If they get under your arm you're screwed. Two, a good counter is for the person in guard to just switch their hips back and get you off balance. But if crush the persons hip there isn't much for them to do. Besides learning from my instructor, I took things from thee videos below to throw the way I do it together. In the Gi i dont completely underhook the person but I grab the seam under their armpit palm down then twist my hand so if I let go w/ my thumb I would give a thumbs up, it makes a tight grip. In no gi I do hug the shoulder and upper body. Always make sure to keep your head tight to their side on the passing side so it keeps everything really tight and blocks the non passing side counter by your opponent. All of these videos are in Gi, but the pass is easily transferable to no gi grips and hand placement.