Start with a dual filter, then. Something like the Intellijel Morgasmatron, which can work as a stereo VCF but which ALSO can work as two separate VCFs. You can also use this as a "mixer" to go from two sources to a post-filtered "sum" output. This is what I would suggest, as these filters have plenty of different modes as well as separate modulation paths...which, again, you can apply to BOTH filters if desired.
-- Lugia
So glad somebody made this recommendation to me ;) I have Sirius' Veil sitting between my Void Modular Gravitational Waves on one side and Instruo Ts-L on the other.
JB