A more sophisticated way of reproducing the liquid quality of paint is to use the ArtRage app, which has a broad selection of tools designed specifically for simulating traditional painting techniques. For oil painting, you can choose to digitally squeeze tubes of paint directly onto the canvas, use a palette knife to spread the paint, or even use a paint brush to apply precise brush strokes.
The oil painting brush has a number of variables that give you incredible control over the strokes you make on the canvas. You can specify the size of the brush, the pressure of the brush strokes applied, how much thinner you would use to dilute the paint, and how much paint you want to load onto the brush for each stroke. There are also a few check boxes to make the paint automatically dry after each stroke, clean the brush automatically, and to choose between a stiff square brush or a softer rounded head.