All of SIG's color dope was blended with their Litecoat dope, which is a plasticized, low shrink butyrate dope.i think all of their dope was repackaged Randolph's, so I think their butyrate dope will work fine. Do a search on the main and finishing forums and I think you will find more confirmation.
   Type at you later,
   Dan McEntee

Sig dope has a different smell than Brodak dope or Randolph dope.  Does this mean that the components are not compatible with each other?  I can't say for sure.  All I know is that I have used Randolph butyrate thinner with Brodak butyrate dope.  And, Brodak butyrate thinner with Randolph butyrate dope.  No problems.  I would not try to use nitrate thinner with butyrate dope.  I have never done that, but something tells me it would not turn out very well.

Pour out a little bit of that Sig Miami blue into a small jar and add some Randolph butyrate thinner.  Spray or brush it on a test piece.  See if there is any adverse reaction.  Better to test it yourself this way rather than ruin an entire paint job.