I have some cheaper acrylic slate grey from Americana that I think I will use to prime. My renegades will have many greys as well, so I may as well prime in grey. Then I just have to find something to seal with after!
As an aside, I am planning a grey clothes, silver-ish armor, darker look for my renegades. Any tips for how to spice it up with a tiny dash of color? I was thinking about a little bit of OSL scorpion green on light sources...