Rear Fender Install

Hudson49

Hi guys. I have a 49 Commodore and had the rear fenders off for some body work. I re-installed and moved on to other things. Now a year later in trying to match up body lines I had one fender off again. Even though I used seam sealer between the fender and body I see a lot of dust has gotten in between the two body parts. So I am looking for some advise. I could the seam sealer again as I reassemble things or I could put fender welt between the two or ???

Anybody have an advise? Thanks