I do give my chickens some turmeric. It can be expensive, but I can get it at wholesale prices through a co-op in my town.
I put it in a wet mash. I make a special super-duper, full-of-special ingredients wet mash that I give at least every few days as a treat. I can't give you exact proportions of turmeric to other ingredients because I'm not too precise about it. A put a few spoonfuls in my big pot of wet mash. However you feed it, you'll have to mix it with something else to get them to eat it. They seem to avoid the wet mash if I put too much turmeric in it.
I have read that it is a good immunity booster and has antioxidants and ant-iinflammatories as well as xanthophyll (xanthophyll helps makes yolks that nice golden color), but I don't think it's a be-all and end-all cure your chicken of anything kind of ingredient.
Did Peter Brown give you any info about how he recommends feeding it?