Artrage oils drawing from several years ago. This is the free version of the app. You only have the oil pen tools but it certainly can be used to create interesting effects. I like this a lot, I used the metallic option to give it this sheen. If you tone down the metallic effect the colours become paler and you can draw over the darker parts (where I have outlined the bird) as it seems to be more opaque and covers over the darker areas.