In my opinion, weather modification does work. However, wxmod won't work if you don't have clouds that can produce precip...
I remember running under a line of cu, dispensing AgI from burners under our wing. At the end of the line of cumulus, we did a 180 and saw the first cloud had a rainshaft under it. Our ground radar reported that they could see echos forming where we had been seeding.
Haven't seen the Discovery Wings show (no TV) but noted some differences between our operation and what Bazzaman96 describes.
In our op, some aircraft flew under the feeder clouds, dispensing AgI from underwing burners into the updrafts. Another aircraft flew at the -10C level (usually 17,500 - FL210), dropping either dry ice pellets or AgI flares into the tops of feeder clouds. We avoided the center of the storm like the plague - as mentioned, severe turbulence as well as the fact that seeding is ineffective there.
The Alberta operation uses Piper Cheyennes, and
this website may have some interesting information, as well as more info on the Alberta operation for you.