1. All the images used for brushing will be resized/ cropped to 512x512 pixels..so if you want a part of the image to be used just crop that part as a square.
2. Basic brushes are good for "stamping" images. (you can use whatever you like but my favorite is basic number 3) Think that the "Edge" slider controls the border of strokes. Experiment with that...
3. Try to slide your finger without raising it for positioning the stroke..it is a weird way of brushing!))))..but it works ..sometimes. The brush always uses the colors from the source image, so you don't need to erase before brushing again.
4. Save often, you can always blend and mask the parts you like later
5. Don't worry about "bad" results, think about he brushing result as it was a sketch..an incomplete piece.. fix the colors and details later, it is almost impossible to achieve that with the brushes..
6. Brush images with tiny details and patterns are perfect for this kind of work as they will bend in soft shapes as portraits.
7. Brushing is not the hardest part, but fixing later the result. Tone colors, High and all the colors presets are there to help you.
8. Have fun)
Similar result image: