Back in the day I've been using this technique a lot and I feel like it's the only thing that's missing from Artrage. Currently watercolors just smudge the pastels and it doesn't look very nice. IRL oily materials reject water, that allows to paint some segments or contours with oil pastels and then work the rest with watercolors or other liquid materials. That creates a cool effect with the oily areas staying mostly unaffected and different while having some dried drops of condensed liquid watercolor. I wish Artrage would detect the difference between oily and watery materials to allow using that powerful technique.