I have been so obsessed with the act of applying thick paint that I've forgotten to mention that nearly all of the techniques outlined in this blog are equally applicable to painting thinly.
In fact if a painter wants to simplify the painting process one of the best ways is to keep applications of paint thin. Here is how the process would work if you want to paint thinly:
Tone your canvas (I prefer a coat of value 4 Red Iron Oxide). After the tone is dry draw your composition on the canvas with a dark piment (like Transparent Red Earth) thinned with ample amounts of paint thinner such as Gamsol (I prefer Gamsol because of its low evaporation rate which makes it less toxic). This layer of watery paint acts as a monochromatic drawing or under painting. Mix up a tone to match your toned canvas and use this like an eraser, working back to the color of the toned canvas to more clearly define negative spaces. Let this layer dry.
On top of this now dry layer start painting very thinly in approximate hues. I might mix a medium like Gamblin's Neo megilp into the paint to make it not only buttery but thin as well. It will also make the paint dry a bit faster.
I will continue to add paint into this layer even after the paint is dry. I have referred to this in previous videos as a full value, full color under painting. If I start to get a dry brush or excessively scumbly appearance I will let the layer dry and oil up the canvas. Since I want to keep the layers of paint thin it is not necessary to oil up the canvas with a thick medium (like my usual G-gel). So I would probably use just a thin layer of Neo megilp. Some people might use Windsor and Newton's Liquin although for me this medium seems a bit too thin. But many people use it with great success.
At this stage I oil up the canvas, paint into the couch (the layer of medium), let it dry and repeat this stage as many times as I need. Since you're building up very little texture you won't have to scrape the canvas to get your next layer of paint flat.
As you can imagine not having to worry about a thick buildup of paint makes the process considerably easier and is recommended for those just beginning to work with oils.
But remember even if you are painting thinly you can still load your brush with broken color. If you have enough Neo megilp medium in your paint it will actually be very difficult to build up excessive texture.
Keep this process of painting thinly in mind as you design your painting career. You may find it easier to start painting thinly and gradually work toward thicker paintings as you become more experienced.
Brad Teare April 2012