If you take acetone and clean the epoxy after it has cured.  Then give it a light sanding.  Go light with the dope when first applying it even after you have several coats keep it light.    Take a little time and browse this section on finishing as there are many ways of doing it.   I think are several guys that are masters at this like Randy Powell and others.

I have never had a problem putting butyrate over epoxy-microballoon fillets. These have always been sanded to a nice even curvature, also removing any of that surface stuff remaining on the cured epoxy. I do start by brushing clear only on edge portions first and letting it dry and do its initial shrinkage. Then I brush to fill the center. Sometimes I do this twice or three times, always letting it set and shrink. I don't know whether this is really necessary, but I wouldn't brush on a thick coat to start. Then I spray.

I have also finished fuselages, stabilizers, and elevators with .56-oz glass and epoxy and sprayed on butyrate, without primer. I had my first problem this summer, when clear butyrate laminated on a small area of my elevator. The rest of the plane - stab, fuselage - is fine. So the sanding with, say, 400 grit is recommended.

The pictures show what I did on the last model. The fourth picture is made up to show shaping. This step is really done while the masking tape is in place. The sixth one shows doping the edges first. After that I run the brush down the middle to fill in.

SK

Dennis-

I just use 30-minute epoxy. I add micro balloons continually, until it is difficult to get more in, not a very quantitative description, I know. A surprising amount of micro-balloon powder will be absorbed; so I continue to add it (sprinkling over the surface and stirring or folding it in as the slurry thickens), even after it appears that little more can be absorbed. The working life is limited, but has not been a problem.  The consistency is VERY viscous. I don't use alcohol. The popsicle stick tool works OK without it, and smooths to the point that everything looks like a final surface. As the pictures show, though, even an even-appearing surface shows rises and valleys upon sanding. While setting, the fillets will flatten out some. So the sanding is necessary anyway. It smooths and re-contours a bit. The more micro-balloons, the easier the sanding. The picture shows what the stuff looks like after mixing and using some. I seem always to mix too much, because the volume grows with addition of the micro-balloons.