About the only "Manufacturer" left is Randolph. AS&S resells authentic Randolph's dopes, nitrate and butyrate, tautening and non-tautening, Sig buys and repackages Randolph's and doubles the price, both for the dope and the thinner. Brodak too I suspect.

I buy Randolph's from AS&S (or Sig fromlocal LHS when in a bind.)

I use non-tautening nitrate for bedding silkspan and Ply Span esaki tissues, Poly Span spun polyester covering, silk, glassor whatever over sheeted surfaces. Tautening over open, but well supported structures. Sometimes I'll mix the two types to get just the right amount of shrinkage...depends on my specific application.

I finished a couple models in Butyrate and Stits,,,,,, never again. Now, after bedding the covering in nitrate (it's the lightest method), I'll usually finish in KlassKote epoxy or Omni PolyU car paint. OMNI is very opaque so you use less paint usually, for most colors. My friend Bob Hunt has been using DuPont Chroma color lately and loves it.