At this point, i would continue with what you were previously useing, just scuff the surface up before spraying the latex. Also i'd let the butyrate dry for a day or so or longer before applying the latex over it. I have used Minwax water based polycrylic over the Sig Koverall, then rattle can sandable primer, then latex house paint with good results, but never over butyrate. I use Sig Koverall alot, and am allways trying different approaches to get a nice finish. I hope you let us know how it works out for you....Gene