A seam like that I prefer the Mr. Surfacer 500 method Gamera listed.

G-J,  what I like to do when I am puttying a spot like that is use a bit of masking tape to reduce how much I have to sand away afterwards.  I lay two (or more) pieces down, one along the fuselage side, as close to the gap as possible, and one along the wing as close to the gap as possible.  Then, once the putty has started to tack up, I peel the tape away.  Often, once the putty has dried, I use masking tape again to protect the surrounding area from sanding or grinding.  This way, I get the putty mostly in the gap and not all over the wing or fuselage, saving panel lines and detail.  Not saying you'd not thought of this already, just a suggestion.

In addition to putty, you can fill minor gaps like you show with either white glue, or hobby paint unthinned.  You do not need to fill that seam to make it completely disappear- there would be a panel line between the fairing and the wing surface.

Fastest, simplest way I've found for small seams that need to be reduced to just a panel line is:

1). Lay some Gunze Sangyo Mr. Surfacer in the seam. Doesn't matter which type- the 500 would be better but 1000 works just fine.

2). Wait 10 mins.

3). Take a cotton swab/bud dipped in Mr. Thinner or lacquer thinner and gingerly rub the seam. It will take off the excess and leave only enough Mr. Surfacer to fill the seam.

Wow!

Thanks for the suggestions.

I had not considered CA.  After I finish some of the other assemblies, I'll pick a solution.

I think that the solution depends on whether or not there's a panel line at the seam. If not, your choice of putty or CA with masking tape to keep things focused is fine. If there is a panel line to be scribed after the repair, my new favorite technique is to weld in some stretched sprue with Tamiya thin cement so that I get a new plastic surface to scribe instead of putty, which tends to flake off.

Mike

In addition to the above, at your option, you may also consider thinning your putty with a little liquid cement or lacquer thinner and apply with a brush. I find the thinned putty has better "bite" and can be applied more cleanly and evenly. If you try to apply putty straight out of the tube, it's an instant mess waiting to happen.

Most hobby putties have a tendency to clump and dry rapidly due to the volatile solvents in them. Thinning the putty gives you more working time and less propensity for gaps forming in the putty itself.

The downside is a little more shrinkage, which may necessitate multiple applications, but with a little practice one can lay down a layer of putty over a seam which is the same thickness as the masking tape protecting adjacent areas.

I did a plane model last winter that was like that I filled it with a thick ca let it dry overnight then just painted over glue filled seam the seam dissapeared complety.          aceses5