If you can get Citadel products, you're golden. Their ink washes - what do they call them now, shades? - are the best in the game. And perfect for BT work.
You really want the Nuln Oil (black) and Agrax Earthshade (brown) inks, plus the Biel-Tan Green.
Now remember, with all inks, applying them changes the colour underneath, so plan accordingly and use paints a few shades lighter than you'd normally use. So light greens, sands, and tans are your base colours, and mid-to-darker browns and greens for your camo. Picking up some brighter colours - red, blue, bright green - for details can be fun. And of course always get black, gunmetal (aka boltgun in Citadel), and something to prime with. Now priming is down to preferences - hand, or spray, or black/grey/white - so just do what you're comfortable with. THese days I prime by hand, in light grey - it gives an even base to work off, and I enjoy the work.
For "normal" camos, the brown ink is the key. After you prime your mini, give it a base coat of light brown (sand, tan, whatever). Then apply the contrast colour. Splodges, bands, ribbons, whatever. If you feel like it, doing like Wildonion did and adding a black (or white!) contrast stripe along the edges adds contrast. Don't feel you have to do it all over - just doing the (for example) upper right sides of the contrast wotks well. Keep it thinner than the contrast area though.
I'd then recommend painting any areas you want metallic in black now. It means you can go back with the base & contrast, and clean up all the little whoopsies & ragged edges.
Then, with a big brush (1/3 inch), slather the mini with the brown ink. Like, all over. Have a cloth handy, and wipe excess ink off the cloth. Then use the brush to dab off ink pooling on the mini. This is important, as you'll end up with blotches otherwise. Let the ink pool, keep turning & dabbing, until you're happy all the pooling has been soaked up. Dabbing is better than brushing off excess ink, as you won't accidentally suck ink out of the panel lines this way.
When the ink's dry, drybrush metallic over the black areas you want to be metallic. Colour the cockpit in - metallic red, green, blue is an easy way to get a good effect for minimal effort - and Bob is your gene-father's sibkid!
Then, experiment. Light green with medium green contrast, with a green ink wash, gives you mid green with dark green, with panel lines all highlighted. Mid-green with mid-brown and black ink wash gives a darker look. Light grey with medium grey and a black ink wash gives you urban or mountain. Lots of combos. Remember, this won't give you CSO level work. It will give you great table-ready minis you can be proud of, though!
