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Just out of interest. What colour do you use as an undercoat? Reasons would be appreciated but I'll live if they're not provided.
I voted black, because that's what I start with, but before I start painting an unfamiliar mini I will also roughly drybush it white so as to pick out the detail (which is also a better undercoat for the parts that will receive pale colours, like yellow and flesh tone).
My armies all end up either Black, Grey, Dark Red, or Silver in the end (Raven Guard and Daemonhunters), so Black is simply the only rational choice. Even on brighter stuff, I vastly prefer to prime black, then either work up a gradual highlight (dark blue to light blue for example) or pick out bright areas with white and go from there.
Mostly black as i think it gives a nicer finish and is easier to paint on, However ive started to use white a little more, but like my vote, it really depends on what mini you are painting!
I usually use black as it makes all those cracks and crevices which you would expect to me shadowed dark.
2000pts Chaos Space Marines
Soon to be getting Necrons
I voted black, pretty much because I just have black spraycans laying around and I rarely would need white (or any other colors) I guess.
However, recently I got into Imperial fists marines and as they're yellow, it might be a problem. But thanks to foundation paints, even black gets a decent paintcoverage with brighter colors.
I use black and white. Black mostly, but white when I need to paint soemthing bright, like yellow.
Some swear by a solid, neutral grey as well. It is said to be "the best of both worlds" (ie. the richness of the black and the easy-coverage of the white). I have not tried it though.
I use a Gray primer, Duplicolor Sandable Primer from various autoparts stores. It works great on pewter and don't melt plastic. Aslo, since it's gray, I can go for light or dark colors very easily.
A while back Slorak convinced me to adopt a clear undercoat, made from Folk Art's Glass and Tile Medium mixed 50/50 with water. It goes on great, can be applied with a brush (my fave), dries dead flat, and grabs paint nicely. I know, nobody else here does it, but I love the stuff.
I vote black mainly because all of my miniatures are well, erm, black. I think it makes sense.