I wouldn't say I have it down pat, but I've got it down to a minimum of expletives.
First, I use 3M Acryl Red putty, thinned down with either nail polish acetone or with lacquer thinner. Depends on my mood. I mix it up to where it's more of a sloppy paste - a bit thicker than white glue - then slather that into the seam.
I also work in short lengths...I'll tape off the entire seam at maybe 3" intervals, so I only have to deal with that much at a time.
After the putty's had a minute or so to set up (enough that it can "grab"), I swipe it with either a q-tip damp with NPR acetone, or with a finger (in a glove, of course, that stuff's nasty). As soon as I do a run to a break (say, cowl to canopy), I bust out the sanding tools to knock down the tape ridge. Then as it sets up even more I'll come back with fine and ultra-fine grits to really smooth the seam out.