Smooth Launch Lug Fillets?

Fin fillets are pretty easy. 

Deep launch lug glue fillets are another story.

   

Here's how the first wood glue pass looks after it has dried. You can see the air bubbles at the root.

A second fillet pass and the bubbles are getting smaller.

After that fillet has dried - 

Lightly run the back of a knife blade over the fillet and you might feel some dips. Add another fillet.

After two fillets of wood glue I switch over to the Titebond Quick & Thick glue. It is 3x thicker than standard Titebond original. There's still a small bubble hole - Add another layer of glue. Every additional layer uses less glue.

I roll off the ends with a Q-tip. This tapers the ends at the top and bottom of the lugs.

Here's a smooth fillet on my Orbital Transport Laboratory build.

When white undercoats are first set down you might notice some ridges on the sides of the fillets. After the paint dries, lightly sand the glue ridges down. 

On a model like the Orbital Transport I wouldn't even try to apply a glue fillet in the wing/tube joint. 

You would have to apply too many layers of glue to fill in all the bubbles in the fillet! That's a lot of extra weight on a glider.