For the most part I just buy the "academic" grade brushes from art stores. Middle of the road and usually $6-10 each. Get the 3 main brushes for models (basecoat/wash, detail, and fine detail) for $20-30.
If you aren't an expert grade painter you wont notice much of a difference with high priced professional grade brushes.
I'm still using up old
GW paints so I don't know the names of the current equivalents.
For my guard which is similar to
GW's scheme I use commando khaki for the fatigues, tallarn flesh (foundation) for the skin, and gretchin green (foundation) for the armour. I then give the entire model a wash of gryphonne sepia.
Highlights are done with the initial colours since they match so well but are still lighter because they're over top of the wash.
After that I just paint details. Guns are black with medium grey highlights. Metallics are boltgun metal with a black wash.
There are a lot of shots of my guard in Crabblezworth's little-camera-big-results thread here:
http://www.dakkadakka.com/dakkaforum/posts/list/120/439793.page
My models should be obvious since they are the only ones painted in the
GW colour scheme.