I use Guterman on the cone. The price is pretty good when you buy it that way. United Notions has had it back-ordered for a few months. I'm hoping we'll be able to get it again, in March. It's 50 wt, 3 strands.
If I could afford it, I'd use Mettler Silk finish all the time. It's also 50 wt, 3 strands, but it's been "gassed" to singe off the fuzzies -- like Aurifil.