Epoxy is tough, but also the heaviest possible method.

Right now I'm doing watered down Elmo's wood filler.

I've done the sticky paper and glued edges. Good results.

I scored a bottle of AeroGloss Dope Sanding Sealer a few years ago.

I crack it open and take a whiff and it brings me back to my teens building balsa model airplanes.

BTW, you can make your own sanding sealer like AeroGloss.

Nail polish and baby power.

A 90/10 mix. Give or take a few.

Clear Nail Polish is nitrocellulose "Nitrate" dope.
While it will work in a pinch to make Balsa Fillercoat when mixed with Talcum, Clear Butyrate dope for the base is better.
I don't know of a way to make home-broo Sanding Sealer, which is a mixture of "plasticizers" dissolved in Butyrate Thinner.

I suspect Aero Gloss Sanding Sealer is Polystyrene dissolved in butyrate dope thinner and clear dope.

I use Brodak, but it should just be “butyrate dope sanding sealer”. It’s all about availability for me. And enamel primers suck, they take too long to dry. It’s gotta be lacquer-based primer. Dries fast, sands easily.

Brodak Sanding Sealer is 99% as good as the old Aero Gloss Dope. All Brodak is actually re-packaged Randolph Dope.
Sig is ok, but it needs at least 1 part thinner to 2 parts Sealer to thin it. I do not know who makes the dope products for Sig or if they make themselves. Their sealer is definitely different from the Brodak products.

Here are the SDS for Sig Dope and Aerogloss sealer......

Randolph (which produces Brodak Sanding sealer) has discontinued making plain sanding sealer. The replacement is Rand-O-Fil Silver. I asked Brodak what the difference is and the response is that is supposed to be same but silver in color.

Has anyone tried this and how does it compare to the original?

That is a bummer, oh well Sig it is.......Rand-O-Fil Silver is basically dope with Silver pigments added. I don't want to mess with sanding silver dope, don't know why they did this but I am sure they have their reasons. Normal balsa sanding sealer was nothing more than dope with an additive to help with sanding. The additive was not really a filler unless you bought Aerogloss Fillercote. I have used regular dope to seal and fill balsa grain for years with no issues.

Sanding Sealer is basically just clear butyrate dope with white styrene dissolved in it.
You can make your own easily.
Balsa Fillercoat is clear dope with talcum powder dissolved in it. Good luck finding Talcum Powder anymore. Corn Starch can be used instead of Talcum.