Mike,
I'm not familiar with that Spar Varnish. I have used water based Kilz, but never on lures.
I used to use either Minwax Polyvinyl or Minwax Wood Hardener, and then oil based rattle can primer, two coats, wet sanded.
Then the Createx, heat set after each coat. And then topcoat.
With the Wood Hardener, I soaked it for five minutes, then let it dry/off gas for a couple of days, hitting it with a hair dryer occasionally to drive out any trapped solvent. The Polyvinyl was water based, and dried overnight.
I found I needed to drill all holes for my hardware before I sealed the wood, to let the sealer into the wood as deeply as possible, without soaking so long it got saturated and lost buoyancy.
And I would run my screw eyes in, to tap the threads, and then run them back out, coat the screw with crazy glue, and run it back in again, to reseal the threads and lock it in place.
I'm not familiar with Veranda, but Trex is too heavy for lures, unless you're making sinkers, as in lead.
AZEK is buoyant, and there is sign making PVC called Sintra, I think, that's also buoyant.
Buoyancy is important, even in sinking lures, because it lets you position your ballast low in the bait and toward the front, to keep the lure upright even underwater.
I never put ballast in my tail sections, because it kills the swimming action.
Hope this helps.