My technique
•   Seal balsa w/ Z-poxy, block sand with 240
•   Apply 2 coats Nitrate
•   Light block sand with 320 paper
•   apply CF matt. I use either pure thinner or 90% thinner  (I use nitrate thinner, but I am told that butyrate is fine also)
•   Overlap on bottom of surface, not the TE.
•   Use torn edges at the overlap
•   Add CF matt one side at a time. 
•   After it dries, kiss the edge lightly with say 400 paper, maybe two passes.  Just making it fair smoother to the balsa.
•   Add 2nd piece to bottom of surface.  Torn edge also.  ½ “ overlap is plenty.
•   After it dries, kiss the edge lightly with say 400 paper, same as above.
•   5 coats butyrate,  begin adding a little zinc Stearate in the 3rd or 4th coat. Do not sand until maybe the 4th coat.  Any sanding is very light  (400 grit paper)
•   You can add more clear dope and Zn Stearate depending on the results you are seeking.

Do not thin the Zpoxy, it’s already quite thin.  Properly applied there will be essentially no zpoxy on the surface.  I don’t think it would adhere the CF


Do your own experiments if you wish.