Know the question was not asked of me (thought you wouldn't mind hearing how different people did theirs) - but I primed mine with brush on railroad Floquil grey primer - this is thin enough and gives a great base for smaller figures. For larger figures, I use Tamiya Fine Spray Primer. I did try to clean up a few seam lines prior to priming but you will see more after the priming and you can clean again. I chose to leave the base the color (survivors) of the plastic to match the color of the cards in use - found this to be most useful in the game.
As far as the plastic goes - after the primer is added to the color plastic you will see great details and I had no problem using Vallejos, Reapers, Andrea, Scale 75, or GW metals on the figures.
If someone can tell me how to post a picture of some of my figures here, I'll be happy to or you can send me a private message with an email address and I'll send you some picts.