I still have issues with image resolution in the blog posting, but I have settled on sketchbook pro as the app to learn, just scribbled on a photo to experiment. Artrage is noticeably slow in comparison, and also has fewer features. I don't think either offers sensitivity of brushstroke, but SBpro makes a very nice mark that simulates sensitivity to pressure. There is a free version, so try that for yourself, but the app was only ¥600. I do think there should be a palm protector feature, perhaps I just haven't found it yet.