Yes, we've been playing with Fumed silica with other processes as well. It looks promising for many alt processes, including cyanotypes, kallitypes, albumen, etc. We're now just experimenting with another fumed coating (not sure if I am of privileged to discuss it here) that looks to have the same benefits of fumed silica with PT/PD printing, except with a slightly cooler tone rather than warmer which appears to occur with the silica.
It's all very exciting stuff! Thanks for experimenting!