I'm not sure what Sin's recording set up is, but I can ask next time what we might be able to do ahead of time to get a cleaner track.
As far as levels go, the issue I always seem to have if I run an auto volume leveler over it is that it will amplify tiny background noises that made it through the noise filter. And that ends up sounding way worse. None of us are recording in a controlled studio environment, so it's very difficult to catch everything. So I generally just set everyone's levels at the beginning and try to adjust here and there as needed if it's really bad. If anyone has any tips on how to do this more consistently, I'd be happy to hear them.