I was telling the ladies in class the other day that I have a habit of wiping my brush on my hand as I paint. Now, I don't wear an apron, and a paper towel can mess with the water flow I have going on my waterbrush. So what to do - use the hand.
Now that's not a bad habit as such, I mainly use watercolors, Inktense or H2Os when doing this so it washes right off. Not a problem unless I run out of the house on a quick errand after forgetting to wash it off!