That's the way I do fine panel lines too Glenn, although I mainly use gloss varnish and talc. The paint and talc is better, as it shows up better, so you know what you've filled and what you haven't - if that makes sense. The gloss varnish and talc is good for finishing over a painted area, such as around a canopy. Another method is to use PVA, wiping off the excess with a wet finger tip, although this would mainly be used in fine seams and joints, such as wing root joints, windscreen to fuselage joints etc etc.