Basically, tools are the most important stuff working with styrene. You'll need a good batch of X-acto knife (don't cut corners, invest in the good stuff), steel rulers (speed square is a very good tool), a cutting matress, a special styrene cutter for breaking off styrenes clean (photos later), glueing clamps, abrasive set from Tamiya, and for the small parts tiny diamond files from Gameswork Shop. As well as polystyrene glues.
I don't do anything like the same amout of it as the guy in the youtube video, but the amount tools we have in common is uncanny - right down to the identical orange-handled angle cutters.
I find a digital vernier essential too, for accurate measuring. I also have a variable angle, somewhat smaller than the speed square shown in the video, which does right angles but also other angles and hooks easily over the edge of the cutting mat. A surgical scalpel is effectively an x-acto knife.