Nearly there finally! only thing left is highighting red and a few minor touches llike text on the purity seals.
Learnt a lot doing these minis, hopefully my next squad (a 10 man Veteran Assault squad using Sternguard and Veteran models) will look a little better and will come much quicker!
I'd do washes of black, brown and one of red or, if you have a lot of time, you can do glazes, it'll be much longer but the effect will be a bit better than with washes. Be careful of not shading them too much to keep the shining of metal.
Glazes are a bit like washes but you have to dilute more than for a washes, you must almost not see the paint. As there is less pigment in glazes, you have to do more one to get a good effect.