Having used practically every medium and support available in the last thirty years, I now paint with one medium -- acrylic -- on one support -- Claybord.
This pH neutral, acid-free surface gives firm support plus many working advantages. I prefer painting on the original Claybord, which has a very smooth surface of white Kaolin clay adhered to a masonite panel.
Drawing
Since I despise gessoing and sanding panels, I like that I can go directly to the line drawing on these panels. I use 4B black charcoal, graphite or sanguine conté crayon, and I make corrections with a kneaded rubber eraser, #600 steel wool, or by sanding or scraping.
I sometimes transfer drawings to Claybord from paper or vellum. I coat the back side of the sketch with conté crayon, charcoal or graphite to transfer the sketch to the board. For works involving several elements, I often draw the subjects on separate pieces of vellum, then move them around on the board to discover the most pleasing visual arrangement before transferring.
Painting
How I approach the painting depends on the subject matter. If I can take advantage of the brilliant white of the Claybord, I paint around white areas much as you would with transparent watercolor, perhaps glazing over them later if I need to tone down the brightness. If the subject has little or no white, I paint a base coat of Cadmium Red Medium with a touch of Permanent Green Light, or Cadmium Orange with a touch of Ultramarine Blue, or use a washed background of Sepia. The opacity of the base coat is determined by the number of coats and whether I thin the color liberally or sparingly with matte medium and water.
Claybord Original is very absorbent, so the first coat of paint dries very quickly. If you want to work acrylic washes over the white surface and slow the drying time, try covering the Claybord with a coat of acrylic medium, then use Golden Acrylic Glazing Liquid as a medium. I often glaze directly on the Claybord, but I may do 10 to 20 glazes over one another, totally hiding the brush strokes of the original layer.
When glazing on Claybord, use pure water and do not dilute your acrylics more than 70-80% in order to preserve the integrity and adhesion of the paint film. As a rule of thumb, when I dilute acrylics with water, I add about 1/4 of the volume in the form of acrylic medium, just to be on the safe side.