Tom, I remember using Aerogloss and Pactra sanding sealer and dope to finish my model rockets as a kid.
When I became a BAR some five years ago I went in to a local hobby shop looking to buy those: Nowhere to be found!
When I asked the clerk what builders are using now to fill wood, he told me to "just keep spraying layer upon layer of enamel until the wood is saturated".
Yikes! Talk about bad information.
I suppose you could paint layers of enamel or dope until the wood is saturated and get a glossy finish, but that would not be the most EFFICIENT way to do it. Also not very economical, plus there is the extra weight.
So nowadays, most of us use Elmer's Carpenter's Wood Filler (CWF). Combine the CWF with a little water and create a slurry, then brush it on. Two coats or more, sanding between coats, followed by a coat or two of sandable high fill primer, again sanding between coats. That should do it.
https://www.amazon.com/Elmers-E842L-Carpenters-Filler-1-Quart/dp/B001E5L19O/ref=sr_1_4?keywords=elmer's+carpenters+wood+filler&qid=1562032522&s=gateway&sr=8-4
Reasons CWF has replaced sanding sealer:
1. Availability: Very few places selling sanding sealer now. Brodak and Sig are a couple of name brands.
2. Economics: One small bottle of sanding sealer costs $9. For $12 I can get a tub of CWF that will last me the rest of my life.
3. Volatile fumes: None with the CWF. Water cleanup.
BTW if you are still interested in using sanding sealer I found a recipe for cheap homemade sanding sealer: dissolve styrofoam into a container of MEK (Methyl Ethyl Ketone) until saturation. Solution should be the consistency of honey. I use the styrofoam peanuts that come with my parcels. Use in a well ventilated area or with a respirator. Disclaimer: Use at your own risk.Fumes are toxic. Also use a glass container and tight fitting metal lid. MEK will dissolve many plastics and synthetic rubber gaskets. Note also that there are two kinds of shipping peanuts out there: don't use the soy peanut, it will not dissolve in MEK.
Seals like liquid plastic. Oh wait, it IS liquid plastic.
And, there is a safer substitute MEK at the big box stores. Haven't tried that yet.
Cheers.