I have petal dust to paint these little white flowers...is it equal parts of water and dust?
As far as I know you can't mix the two. Try using any clear liquor like vodka. If you don't have that you can try almond extract, clear vanilla extract, or lemon extract. You want something that will dry quickly and not gum up your fondant or gumpaste. You can also use it dry, and then steam it a second to really make the color stick and look more natural.
As far as ratio goes, I just mix enough to get it like a very liquid paint. HTH
I had the same question not long ago and all the great cc'ers came to my rescue. Check out this thread: