I use artist oil paints for the DOT weathereing technique. You must have a barrier, meaning if using oils over enamel then you need a clear acrylic over the enamel. I prefer to do the DOT techniquee over a flat acrylic finish cause I find it creates a better effect and blends easier and better than over a gloss coat. Over enamels I use MM clear acrylic flat as a barrier.
The oil paint is dragged down with a thinner dampened wide brush. Clean the brush in thinner then drag over a paper towel to remove most of the thinner and continue to drag it down on the model till most of the paint is gone, leaving subtle tonal variations. Let the wet surface dry overnight as the thinner will evaporate leaving a flat finish. If some gloss is evident, then spray clear flat (acrylic or lacquer) over to neutralize any gloss.