There is something to be said for using brown as a base color, I've used it on some pirates and I like it. There was an expert painter that I took a class from who swore by gray as a primer, and then would paint a layer of brown on certain items before applying another color like red or yellow. My sense is if you're going to do a good bit of that, why not go the whole way and us it as a primer, then you skip a step on the figure. Probably depends on how much of what colors you're using, because gray does give a certain ability to move in different directions with different colors of paint. At the same time, I've bought multiple shades of brown spray paint to use for horse as well, because I got to imagine that'll make such easier to move along upon, and get them done.
