Having problems trying to get a couple sculpts to low-polycount levels for use in SFM

[system]

Hiyah
So I made some ZBrush models of the Space Ghost gang.

So yeah. I already asked the Facepunch forum and they said

You’d probably want to redo the topology on them with ZBrush’s topology tools or inside 3ds max. After that, it can be rigged in max as well. I’m not sure you want to port models directly from zbrush to source without any work on them first.

So yeah. And I tried the retopology tools (ZRemesher) but the polypaint disappears. The sculpts are also multiple hi-poly subtools, which makes the UV Master break.

Help please.