Thanks so much you guys - I've had so many flops lately and you make me feel that all is not lost!
About the Viva towels, yes they work very well with a minimum of fuzz, especially on the 500 and 600 grit of UArt. For this one I used a little piece of Glad Press 'n Seal because I found in a cupboard in the kitchen and never used it like it was intended. It has a slightly sticky side - not good - and a slightly textured side - very good for lightly rubbing in a layer of pastel with no loss like you get with a paper towel. It's kind of a pain to use though - it crinkles up very easily. I just make a smooth spot with it and leave it on my finger until I'm done. If you have some of this in your kitchen you can give it a try but I'm not saying it's worth a trip to the store.
Here's what I learned:
Don't rush the underpainting. In a scene like this where the light on the branches was the main attraction, I needed to know where the lights and darks needed to go. If I wasn't able to return to finish this my 'color notes' would have been a big help. By placing the right colors on the right value areas of the underpainting I had enough information for a studio finish. I envy those of you who can do a loose watercolor underpainting and then get to work. I guess I need more structure.
Don't go on autopilot. The upper branches were getting as much, or more, bright sunlight than the lower branches - my intended area of interest. I started putting the same light yellow-green up above as I had below and then froze. Just because it was that way in reality did not mean it was best for the painting. I switched to a same-value green but in a more neutral color. I have several that are kind of dull and don't fit with the warm or cool greens. I've read about using the greyer, duller colors to keep certain areas of a painting quiet and this idea is finally sinking in.
Pay attention to weird things that catch your eye. On the sunlit trunk, about 2/3 of the way up, there is a little piece of a broken off branch that had the most interesting orange glow where it didn't seem possible. How could it be orange on the underside when it was technically in the shade? I eventually realized that the color must be reflecting up from the bark of the tree. I had to look really long and hard to see it but it was there. As soon as I added some of that orange to the trunk the tree seemed much more alive. I'm glad I didn't rush and took the time to notice that. This is the kind of thing that doesn't show up in the photo but makes a big difference in the painting.
The more I do this the more I realize that I have lots of learning to do. I will try to stop beating myself up for not painting as fast as others. Learning to paint better, not faster, is more important to me right now.