MA is my first attempt at 15mm and also first attempt at painting figures that are multiple based. For my barbarians, I've done the following to get them painted.
I've got a bunch of coffee stirring sticks from work (about 5 inches long) and glued them onto cereal packet (did 2 by 1 sticks) and cut around the sticks (leaving a bit of an edge around them).
Stuck some double sided tape over the sticks and then staggered my barbarians across on the top part of the tape (can get about 8 models per 'stand' in this way).
Makes it easier to quickly spray the undercoat on them (and gets good coverage of front and back) and also gives decent access when painting. I've used fairly strong double sided tape and it's doing well - haven't had models falling off during painting.
Hope this is useful