What the painter told you is call white wash it is used to highlight details in the work piece or to help something look aged. There is no formula to mixing it. I use it from time to time I add water and try it on a scrap piece of wood till I get the look I want. If you want to pickle something minwax , Old Master and some other stain companies sell a white pickling stain that works very well. I use it a lot on the inside of all wood cabinets to lighten up the insides then I put a couple of coats of poly over it.On some woods like red oak it is good to bleach it first because it can turn the pickling finish pink.