Really? As I understood it, the Shinigami were using Reiryoku, the actual Spiritual Power, to solidify the air, while Quincy were using Reishi, or the actual particles themselves. As far as I was aware, I don't think Shinigami have the ability to actual directly manipulate particles, bar obviously certain special abilities centered around manipulating matter.
Though admittedly, Zangetsu said "Gather spirits under your feet" and didn't make any distinction of what he was talking about for that particular bit. Could certainly go either way, both Particles and Energy is supposed to be ambient after all. :hmm:
I suppose that's another reason going into the whole Reiryoku/Reiatsu/Reishi distinction is a confusing mess since it was left aside for so long, despite being one of the more interesting parts of the series.