I did go over the technique on filling without sanding, using putty, fingernail polish remover, and so on. Your directions were great to get there.
What I didn't explain very well....is... I think there should be a 'line' or 'seam' where the fuse meets the wing root as the kit is designed.....a thin line, not a huge gap as I had......I would fill using the above technique, then upon completion, try to scribe a fine line in the middle of the filled seam....kinda hard to explain.
But.......the gap is now not so bad.......while working on the lower area in front of the wing, sanding and so on, to improve the fit, I noticed the wing root gap was opening and closing and I realized that I did a poor job of attaching the wing assy. So, I added a little solvent cement and closed up the gap some, and it made a big improvement. The dihedral increased slightly, and I think it looks better, more accurate.
Still, after I sand off the crazed paint and look closely at the gap, I am sure I will be doing some filling, using the technique you suggested.