I suggest the following:

Sand as much of the glassing job away as possible without getting too badly into the wood.

If the low areas can be seen without a primer coat, fill and sand them with a lite weight filler, if you can not see them just proceed as indicated. You will get the highs/lows further on.

Put on ONE coat of a sanding sealer. Whether or not you do the whole thing will depend on the amount of bare wood and filler area you see. You may be able to get away with just "spotting" them if it isn't too extensive.

LIGHTLY sand the sanding sealer with 220 or 320. All you want to do is remove the fuzzies.

Use 1/2 OZ (.5 oz ) fiberglass cloth. Lay the cloth over the wing (stab, fuselage, elevator, etc ) and using a WATER BASE polyurethane and a FOAM brush apply a coat of polyurethane to the fiberglass. You want to work from the center of the cloth out to the edges of the cloth. Brush in ONE DIRECTION only. Make sure any overlap areas, overlap by at least 1/2". DO NOT SAND AT THIS POINT.

When this dries, apply a coat of water base polyurethane mixed with microballoons to fill the weave.

Wet sand this with 220. BE CAREFUL, you can easily sand through the fiberglass cloth.

CAREFULLY check the fiberglass to make sure the weave is filled. If it isn't filled, give it another coat of poly/microballoons and wet sand again.

Now give it a LIGHT coat of primer and block sand to show up and highs/lows. Fill any lows with lite weight filler.

Put ONE coat of sanding sealer on any filled areas and LIGHTLY sand.

After all this is done, spray ONE COAT of water base polyurethane on the surface. When it dries you will be ready to prime, detail and paint.