What are you asking specifically? Do you just want to try some more colours, or are you wondering about the way they should be used?
I pretty much stick with nuln oil and agrax earthshade for washing and use regular paints for the rest of the detailing. They can work quite nicely together when applied in successive layers. Nuln oil first, and then agrax in two thin coats to dirty up the black a bit. I suppose I'd use a similar approach if I was doing a more vibrantly coloured base by replacing the Nuln oil with a bright wash of the right colour and then overwashing with something appropriately grimy..
There seems to be a bit of a trend about at the moment for doing whole models with just washes. I dipped my foot with a Chaos warhound and had reasonable success with my standard approach of multiple thin layers to build up tone. But I've seen people painting entire squads by just base coating and then heavily washing with a bright wash and it doesn't do it for me I'm afraid.
This is the beast in question, the body was purely washes over a base-coat, about seven layers of variously nuln oil, agrax and possibly some reikland, I forget now..
Is that of any help? If you're a bit more specific you'll probably get some more usefull advice..