Painting the seam of an already painted model

I realize that I've probably done this backwards, but can anyone offer any advice, short of start over? Otherwise, I guess I'm on my own. Surely, someone has run into this situation before...

You can mask outwards of the seam. When you tape roll up the edges of the tape so when you spray it will create a softer edge. Also spray away from the tape not into it. This is an old automotive paint trick for blending paint

For a metallic finish, try to mask along panel lines.  Any difference in finish actually looks fine.  In fact, many times with a NMF I do some panels after I do a complete coat.  I mask them off with Post-it notes and spray a thin coat over the original coat.  The thicker coat on those panels will have just a slightly duller sheen.

 

Thanks guys! Those are great suggestions!! It's been over 50 years since my last build. Lesson learned: There are good reasons to do things in a particular order (you'd think, as an engineer, I'd know this!). Next time, I'll fill and sand, THEN paint. I think I was hesitant to do this, as I'm still in rattle-can mode and couldn't bear the thought of the complicated masking job required of painting after assembly. That was before the discovery of pre-printed masks. Ah well, live, learn and enjoy the hobby!!

I think you need to follow the above this way. mask all the way out at the next panel line away from the seam. This can still be clear of the window.

I've never quite done whats being suggested, but I've done a version. On airliners with a colored stripe around the windows, I have painted the color on the individual sides, thn installed the windows and masked over the whole stripe area. That also avoids putting tape on metallic paint, which can really be a problem.

Any type of filler MUST be sealed first with clear gloss like Alclad or Testors clear coat otherwise the metallic finish will look different over the filler. As suggested tape up to panel lines and do your repairs. Taping over the metallic finish should be ok since you used the Metalizer Sealer but tape with caution .

I avoid using fillers when doing NMF. I use either Tenax or Plast I Weld to run along the seams then squeezing them together forcing some of the melted plastic to form a slight ridge along the seam. I set it aside to cure a few hours then use sanding sticks to get rid of the slight ridge leaving a solid invisible join.

PJ makes a good point. With metal finishes, often the effort to hide a seam is worse that the clean joint, if there's no gap.