I have all 6 colours of woodland scenics stuff, you cant get a GW static grass look by using a mixture. The woodland scenics stuff are all kinda 'muted' in colour, mixing them together can give you a very nice realistic look, but its overall kinda 'muted' for lack of a better term. Kinda like how vallejo model colours are to the game colours.
If i remember correctly, I use a mix of about 3 medium green : 1 burnt grass : 1 honey of the woodland scenics stuff. I will see if I can dig up some pics with any decent closeup shots. I actually prefer the more realistic colours of the woodland scenics but thats just me.
On grass, I found this system works best for me:
1. Choose the predominant color you want to use. Buy a bunch of this, and use it as your flock.
2. Buy several shades of spraypaint.
3. Spray away until you have the desired texture and effect.
I found this was a greay way to throw in patches of "dirt" or paths through the grass too.