I usually use a brush on primer for Bones figs, the plastic on them is a beast to work with. But if you have a good primer it makes all the difference. I like Citadel's.
Do you use a spray primer or a "brush on" primer? I don't own any of the BONES minis yet, but I've been considering them because I would have expected the wear to show less on plastic miniatures than on metal miniatures.