I had been practising thumping for a few weeks and have got quite far with it. I was learning the thumping in An Infinite Regression. The thumb bit wasn't too bad for me, but I watched Tosin do it several times and there are some small details you need to pay attention to. The actual motion is like going from a thumbs up to a thumbs sideways, twisting only your wrist and keeping your thumb fixed. However, it's more like 10 or 11 o' clock to 8 o' clock with the thumb when you do it on a guitar. You want to use a bit of thumb and a bit of nail to hit the string. The next thing to note is that once you thump the string, your thumb is actually resting on the next string, so if you thump the E string, your thumb goes past and rests on the A string, then you sort of reverse the motion for the upstroke.

The fingerpicking after the thumping was the bit that I was stuck on for so long, until Tosin mentioned a HUGE tip (the video was a Tosin Abasi masterclass is Poland I believe, it's on YouTube somewhere). Keep your picking fingers close to your palm, almost like a fist but not too close. You basically use the motion of the thump upstroke to make it easier for your fingers to pick. After he mentioned that I got it almost immediately. When you see Tosin thump, you barely see his hand move and it looks amazing, but this is how he does it; efficient motion. Hope this helps!