Here's another thing to consider about Duratex or any other water based product. It will swell wood fibers and likely kinda lock those fibers in their swelled state. It's the nature of all finishes to some extent, but water is especially so. Duratex doesn't sand well because it's sorta rubbery in nature.
One way to deal with the issue is to seal the surface before applying the D-Tex. Mike suggested epoxy, but other things could work also. Shellac is a favorite of mine because it's easy, inexpensive and dries fast. I rarely use it as a finish topcoat, but rather a sealer and barrier coat. Another single component sealer I use is Zinsser oil based Cover Stain. Dries fast, powders when sanded and can be had in spray cans.
Any of these base coats should make Duratex move even in sheen, easier to apply and require fewer coats.