What ratio of water to latex paint do I use to get a milk paint effect?

Old camp needs ceiling brightened. It is plywood that has never been painted. I got a response that I could use latex paint watered down, but no ratio. Help?What ratio of water to latex paint do I use to get a milk paint effect?
Mixing water to latex paint will give you a ';wash';affect, like a white wash over a wood chair. The milk affect you speak of seems like it would be better accomplished by mixing a clear glaze with your paint. I would suggest you speak to a paint professional at a paint store or a home improvement store.