I've been doing this for years, but when we were newlyweds, and poor, we used this same method in our remodeling:
I shouldn't say we, because I had nothing to do with this:
We bought an old house and really wanted to paint the green living room walls. So, we painted using Sears paint, $10 a gallon. He got the room nearly done, and decided he was going to make that last gallon of paint last to the end, so he added water!!!!!
There were a few spots that the green could be seen through the tan.
We laugh about it now