I am a professional Australian watercolor artist and tutor. I intend to use this Blog to put down in writing some of the things I have discovered about watercolour and to promote my work and activities as they develop. My work can be seen at my companion web site http://www.joecartwright.com.au/
Sometimes when you have just about finished a painting you may find yourself wondering if you should put in an extra tree or other object but you are not quite sure.
In this case you can use a piece of printable clear plastic, which your local art supply store should stock. Place the plastic over your painting and paint in, with watercolor, the object you are considering, onto the plastic. If this looks good then go ahead and paint it on the original - otherwise try something else or just leave it as it is.
This gives you a lot of freedom to try various things without damaging your painting.