I don't have a drywasher or anything. We were visiting friends in the desert last fall and there is a very deep wash behind their house. We didn't have a detector with us, and it was getting dark. But we hurried and filled two 5-gallon buckets with root, rock and sand to take home to play with. Found what appears to be small garnets. After panning about half the dirt, we got too busy. I was going to dump the second bucket but decided to swing a metal detector over it first. Bing! Saving it to play with on a rainy day!
Dry washing is not as effective as a sluice but if there is no water it is not an option to use a sluice so probably more effective there. lol Yes, once you get done with a sluice or drywasher you would want to pan the concentrates....unless, of course, you were finding so many huge nuggets you didn't care about the small stuff. As with any piece of prospecting equipment you will find some models work more efficiently for you than others depending on conditions where you are and your experience with the equipment. I do not know a lot of folks that use drywashers but I am sure there are some and we could benefit from their knowledge if they had an area to share it.