you dont have to go 50/50 its better if you go 35-40% the paint is not really that thick but it cuts down on the saggs and runs. if you go 50/50 you are cutting the paint down a whole lot therefore giving you more runs and sag. i have been doing this alot and i use about 35% thinner and roll all the paint out of the roller and going back over it to work out some of the orange peel with the weight of the roller