Just start with a dark shade of green and progress into lighter colors. Personally, I do a base coat of Calliban Green, a central highlight of Warpstone Glow, some further highlighting/glazing of Moot Green, and finally a glaze of Waywatcher Green over the whole thing.
I am a fairly new
40k player and painter, and don't by any means consider myself to be a good painter, but I've found that my "technique" works for me to achieve a rough tabletop standard.
Here are a couple of bad iPhone pictures with a paper backdrop. Sorry I haven't based them yet!