| I studied with Gary a few summers ago in Victoria, so I figured I'd throw in my 2 cents here. (First post!)
The Bernardel is great for learning the slow-bowed, close to the bridge playing that Gary is known for. This technique is great for solo playing, as it does a great job cutting down the "muddiness" factor while increasing volume, which I believe knocks out 2 of the 20,000 reasons the double bass isn't commonly considered a solo instrument. Playing closer to the bridge with a bass rosin by itself can achieve this to an extent, but the sound produced is much more pleasant (clearer, sweeter, doesn't suck) using the Bernardel, esp in the higher register.
The downside to using the Bernardel is that it makes advanced bow techniques like the off-the-string strokes or just fast passages much more difficult to execute. Gary has a nice, well-projecting sautille stroke (Goens - Scherzo), but I wasn't too impressed with his spiccato. I think mixing with a bass rosin is more practical to give the bow a better grip of the strings (Daxun apparently mixes Kolstein bass and Pirastro cello rosin).
I personally went back to using pops after the experimentation though... I also doubt many orchestral players use cello rosin, since spiccato's kinda important. | 
