Rather than reinventing the wheel, here is a fabulous tutorial by Jerry Jobe. He does end it with negative comments such as how long the images take to render but I didn't find that to be the case on my iPad. I think they have improved that in the last update.
I really do love this app, especial when combined with some others.
A few examples...
If you love impressionistic style art, give Artista Impresso a try.
Have a Happy Mobile Art Monday!
If you're having a hard time with the tutorial link, it's been updated. If it's still not working for you, just Google Appwhisperer Jerry Jobe Artista Impresso.