When I replaced the welting on my p-up, I weatherstrip adhesived (not too much - just enough to keep it in place) the welting to my fenders. Made installation easier and less likelyhood of scratching things up.
Also, since I used a "u-cut-your-own" type, I left enough on the visible open ends to "curl under" the welting so it looks nice and you don't see a "cut" end. I did this at the top of the front grille, top of the cowl, and maybe the back most end of the rear fenders. Everything else is hidden if memory serves me.
Mind you, this is obviously not a triple A rated restored truck - just a nice looking driver and trying to be neat!