Some progress in the past two weeks!
Test fitting:

Last weekend, I've painted the cockpit and the interior of the plane and applied to instrument panel decal. I actually forgot to apply one of the decals right by the side of the seat because I was excited to seal everything in.
Somehow this makes me realize how little detail can be seen on a 1/72 cockpit. Hasegawa's cockpit side walls are empty but it barely bothers me because you can't see much.

After I sealed in the fuselage halves, I did another test fit with a masked canopy.

And as of today, I did the primer application via airbrush. I used Mr. Surfacer 1200 thinned 50-50 Tamiya Lacquer Thinner, and I was very impressed at the result. I had a few rough patches on the wing roots where the primer and air would "bounce" at the corner hence creating a very rough texture, but I managed to sand it very smoothly down with a 1200 grit sandpaper. Mr. Surfacer 1200 is so fine, you can still see the panel lines!

Hopefully tomorrow I'd get to touch up the spots where the primer got sanded off, and maybe I'll try to apply the first base coat of paint!