Generously! Kevin Macpherson said it best when he wrote that we should paint by the pound. I love that idea. Yes my paintings may lack for composition or some other quality, but at least I try not be called stingy with my paint. Like the French who insist that good cooking demands rich ingredients we artists need to be bold with paint and brushstrokes.
The brushstroke is an essential part of This idea. Hold the brush horizantal to the canvas, for example, and lay the paint down in a sideways motion. There should be a textured color note with each stroke. Resist going back over that stroke to avoid flattening it. Use this approach with some variation where necessary, but trying not to lose the effect. A distinct mark of color.
Many a time I have finished a painting dissatisfied with the result. Then to return the following day with a fresh eye and was able to appreciate the music of color notes and texture of the oil paint. It is something that seldom disappoints.
Nature after all is never flat. Why should our paintings be flat?