I watched part of a recent webinar on painting rocks and water, and another on painting skies, and picked up several techniques. The next one coming up (starting May 12th) is on painting grass and snow. I've struggling with snow so will likely participate.
The classes apply to watercolour, oil, acrylic, pastel and possibly other
mediums, and seem to run over 3 Saturday afternoons in a row. DVDs are available for sale following the class for anyone who was not able to take part but wishes to take advantage of the lessons.
Advance sign-up is required, and a good internet connection and sound. No special software is needed - the meeting-based forward will load for you. Again - the online class is free. They make their money from DVD sales following the classes.
If you are interested, the link is: http://improvemypaintings.com/