Basic Canvas Prep
When it comes to prepping your canvas I think the biggest tip that I can give you for actually painting is to be careful with using too much “liquid white”. If you have a canvas that is “too wet” (i.e. too much liquid white), almost none of the techniques will work.
When you use liquid white, you will almost always need to wipe off the canvas with a paper towel or a clean dry brush. Gently and evenly. Most beginners skip that step because it isn’t really mentioned in most of the videos with a few exceptions. So long as you aren’t scrubbing the canvas dry, it should keep what it needs for this style to be successful.
Here is an step-by-step video walk-through of a basic cloudy blue sky. It goes from a completely dry canvas to and ends with clouds (watch with annotations). I rub the liquid white off my canvas fairly aggressively.
Alternatively, you could just muscle a thin coat of titanium white across your canvas which is what I did in the beginning.
Black Canvas
Either buy a black canvas or evenly coat a white one with at least one coat of black gesso. I, personally, don’t like to paint the edges with black gesso until I finish the painting and I’ve let it dry.
If he uses a liquid clear (he’ll tell you), apply it the same way you would apply liquid white- SPARINGLY. I use a linseed oil in place of liquid clear as a cost-cutting measure, and have experienced no ill effects.
Scrub in a transparent paint color as needed, starting with the brightest colors, ending with the darker ones:
Yellow > Red > Blue > Green > Brown
This step is a lot easier with liquid clear / oil on the canvas, but it usually isn’t necessary. If you aren’t sure what colors are transparent enough for this method, try a little bit of paint on a corner of the canvas. If it looks black-ish, it’s good enough.
Next, blend the colors together with “little x strokes”, then take a clean dry brush and slowly go across the canvas in one direction horizontally, then one direction vertically. Make sure you have coated all of the places you need paint, because you can’t go back once you start putting in bright opaque colors. Don’t leave any clumps of color. Remember: this is supposed to be a very thin coat of paint.
This
video that describes a rather lengthy black canvas set-up. You may find it helpful to see how it is done.