The USA Bassballs mod is simple. Open up the pedal. On the bottom left and right of the circuit board, there are 2 internal trim pots that control the sweep of the filters.
Desolder them, and replace them with full-sized pots. Drill 2 holes in the casing, and there you have it.
It turns a useless pedal into something funky and musical.
Sounds easy enough. I'm pretty sure I even have a couple spare pots lying around.
It'll be nice if it really makes it as usable as you say it does. I bought the thing because I wanted to have an envelope filter around for when I need one. But I rarely need one, so I went with the bassballs, mostly becasue it was cheap, and I'm kinda regretting it.

- but it has usurped my VT Bass for tube growl.