In talking about either Randolf or Cooper dopes I have used 3608S for both with equal success for both nitrate and butyrate. HOWEVER - there have been some changes made since I was spraying those brands, so don't rely on this unless you try them first, as suggested before. I still use 3608S for Sig dope and for McFadden and Behlen nitro-celulouse lacquer, but have never used Brodak dope for anything but one guitar a couple of years ago. (Didn't react well with the 3608s at that time.)
Much has taken place in the past few years with the EPA making requirements tougher and tougher on the finish producing companies, so be sure and follow the "try it first" approach.
Blessings,
Will