This starts my playing with another app, Art Rage. It has a real world media metaphor, which makes it easier to understand what the various brushes might do. This one uses the oil paint quite a bit, and the palette knife to mush it around.
I’ve also started using a Stylus Sock Pro. Makes a big difference when I’m trying to get a sharper line or shape. It’s a piece of conductive fabric sewn onto a paintbrush handle. It still has a blunt end, which the iPad needs to register the touch, but it offers more control than fingers.