Agreed, square wave into the Doepfer clock divider, and lower frequencies out from that. I've confirmed this works with my setup.
Additionally what I'd generally want to use:
-- original signal running into a buffered mult, so I can take the source signal, feed it to the Doepfer, but also have 1+ copies to send for mixing etc
-- a mixer to take 1 or more outs from the Deopfer and mix in various ways (with or without the original)