Hi Adam, I agree with you, the oil brushes can be a little tricky to use. Setting the brush loading, pressure and thinner amounts make a difference in how the paint is applied. With thinners set low the brush lays down gobs of paint and when set high the paint lays down thinly. As you brush over an area that you already painted the colors will blend.
With auto clean set to off, the existing color will mix with the new color on the brush and you will have a new color until you dip the brush into the water glass. With auto clean on you get clean paint each time you touch the brush down. It will still mix with the existing color. The longer you hold the brush down on the canvas the more you blend with the other color.
If you set insta dry to 'on' the new color will not blend with the color ubderneath. It covers it. You can then blend this somewhat with the knife.
Best advice I can give is keep trying different things. The oils are nice because you can do a lot of blending with the brush or the knife and get some great effects. Hope this helps. Joe
Give a man a fish and you feed him for a day - Teach a man to fish and he will sit in a boat and drink beer all day! Joe V.