All Poly-Fiber paints are polyester vinyl and remain flexible but don't shrink. Dope shrinks throughout its life as it is designed to do. Epoxies are not as flexible and may crack on open surfaces such as open bays between wing ribs. On any Polyester fabric, nitrate dope may shrink and peel away, unless the dope has completely encapsulated the thread. Dope was great on silk or linen because it was able to attach to all the tiny fiber around the thread.
Polyester is woven from monofilament line, very smooth monofilament line.
If you start with dope, stick with dope. You can paint, prime, prep or ready the fabric in any way you have done it in the past. Just remember, any problems or flaws you may have had then, may present themselves again, such as chipping, peeling, or cracking of the paint. Fabric on a wing does three things for us. First and foremost, it provides the airfoil to make this magic of flight happen.