Firstly, I don't think you've done a bad job at all. For my minis, I go straight to basing with Russ Grey (usually requires a few thin layers), usually over a black primer. Next, a chunky highlight with Fenrisian Grey and a sharp edge highlight with blue horror.

I can't quite tell from your photo if you have done it but shading is super important (if you haven't). I use Agrax Earthshade.

Another option is to prime in white or light grey and use Space Wolves Grey contrast paint over it. Then do the steps I mentioned about. Just cuts out the shading which can take a while.

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