Dianna Shyne studied Russian Impressionism for 15 years and has worked in oils, watercolor and acrylic. In 2000, health issues caused her to discontinue working with oils and turn to acrylics instead.
This is a link to a demo about keeping acrylics from drying on your palette, and here is a page on her website where she does a 30"x40" painting on location.
The painting shown (above) was done during an artist-research project in the Northwest rainforest, sponsored by National Geographic magazine. The artists climbed trees and painted on platforms high above the ground.