greenlake

What are the qualities shared among Baker's, Clayton's, Sedgwick's, and John White's bridle leathers but not present in other English-style bridle leathers?

I can't speak from experience, but if I ever was to make natural dyes or stains I'd pay close attention to chapter five in "The Leather Worker's Manual" by Standage. You can find it legally for free online. Edit: It also has recipes for finishes and many other products. It's a great resource, but many of the recipes outside of the dyes and stains can't be used as-is due to unsafe or unavailable ingredients.

I can't speak for Twofinger, but I've never gotten anyone at Tannery Row to answer the phone or respond to emails or to messages sent through their online site.