1/. Don't use the "decorator's paintbrush," supplied with the bottle, for anything other than flat surfaces, which you're going to press together after applying the glue.
2/. Get an old, or cheap, OO (or finer) paintbrush, and dedicate it only to applying the glue, then practice on some lengths of sprue. Press them together, and take a small drop of glue onto your brush, then gently apply it to the join. Watch the glue run along the join, and, where it stops, apply a second small drop. Note the emphasis on small drops; if you don't overload the brush, there'll be no extra glue itching to run across your model, searching for your fingers. If you have to use the glue for a knife-edged join (e.g. wing trailing edges,) hold the parts vertically, with the fingers/thumb above the point to which you're applying the glue. The glue should run down the join, away from your digits; if it should run across the surface, leave it alone, until it dries, then remove the mark with some very fine wet-and-dry paper, used wet. If you can find Micromesh, the cloth-backed abrasives are so fine that you can bring plastic back to a glossy finish. The same material will remove your fingerprints off plastic, as well; I've removed them from the "glass" front of an instrument, leaving it as good as new.
Edgar