I've used the method "filling seams without sanding" and my firts attempt was well, rather shameful. It was on the Monogram B-29 that was so badly botched after being dropped that i just threw it into the garbage...after i broke it up of course...
Anyway, Im working on a Su-27 and I'm still 'perfecting' the technique, however I the seams NEVER seemed to be finished, and so I don't really have any confidence to move on and say "ok, its ready for painting". They just don't feel right