MX-774 Kitbash Part 6 Seam Filling

Some builder is going to read this and say: "He's doing what?"

I've gone back and forth over the years on the best way to fill body tube seams.
Thirty years ago I used white wall spackle, back when it was real wet and gritty. It was too wet and gritty for the kraft paper tubing.

More recently I've been using Elmer's Carpenter's Wood Filler mixed at the same consistency you'd use on to fill balsa.

I first used small brushes, painting over the seams. Then I'd lightly "squeegee" off the excess with a razor blade, leaving as much as I could in the seam.

For now I use a old, dull X-Acto blade to apply it. I dip just the tip of the blade into the filler, leaving a drop on the blade tip. Wipe off the back side of the blade on the filler jar lip. You won't need all of it.
The bead of filler is set into the seam. I can drag and spread the drop of filler down the seam. The Blade edge easily stays in the seam trench as I push the filler forward and back, in a sawing motion.
You are doing about an inch at a time, then going back for another drop of filler.

Because the filler will shrink when it dries, I don't "Squeegee" off the excess. I simply sand the raised ridge down to the surface. Tube seam widths will differ between tubes, a smaller width seam will hold the filler better than a wider width seam. Let the filler dry thoroughly before sanding.
I use 400 grit on a block to sand off the dried filler. Sand lightly, you don't want to knock the filler out of the seam. Using Carpenter's Wood Filler will usually fill 3/4 of the seam depth. The last 1/4 will fill with spray primer.