I was taught to paint by a professional and when estimating the amount of paint needed, I always allow for a second coat just to make sure of coverage. We interviewed a painter who tried to tell me I bought poor quality paint without knowing where I purchased it, and stated he would have to buy all new paint. He had not seen the cans and was just guessing so I asked him where I should buy paint from now on. It was the same place I had purchased my paint and he wanted to charge me an extra 20 a gallon more than what I paid for. Needless to say, I have interviewed numerous painters and they are not all honest.
To pick the right color for your space, grab lots of paint chips, place them on the wall near the trim, and look at during different times of the day to see how light affect the color. When you’re ready to start testing shades, paint sample colors onto sheets of heavy paper instead of the wall so you can move them around and not make a mess of your walls.
When I had my interior painting done, after clearing out all of the furniture, myself, I also removed all of the wall plates in all the rooms to be painted. They were a beige color and probably yellowed. The wall was originally an off white and I had it painted a light-mid grey, so those wall plates would look terrible. After pricing replacement plates, switches and outlets (Would have been way too expensive to replace all of them), I decided to just paint all of the wall plates, switches and outlets (Used just a black gloss spray paint). I sprayed the plates outside and used a small brush on the switches and outlets. It worked out just fine and the blacks plates, etc compliment the wall color. It has been 7 years and the plates, switches, outlets are holding up well.
Back to the article. You can add water to all latex based paints / thinner to oil based paint. The tinting base has absolutely nothing to do with it. Say you are working outside and throughout the day you have to add a little water to keep the same consistency. If somebody really tried to add 20% to 50% water they no longer would be painting they'd be performing a whitewash or pickle finish.