Answer: Redwood trees grow best in coastal areas where there is a lot of humidity in the air and occasional fog. They like high humidity but I don't think I'd spend my time trying to mist them. What you can do, especially during the hot summer months, is turn a hose on the foliage - mostly to rinse it off to discourage spider mites (they love hot, dusty places and often attack evergreens), but also to increase the humidity in and around the tree. Once every 10-14 days should do it.
As for trimming off the lower branches, I'd wait until next spring. Your new trees need time to establish their roots. Since pruning promotes new growth, your trees will react to pruning by trying to grow new branches instead of concentrating their efforts on establishing the root systems. When you do trim off the lower branches, remember to remove no more than one-third of the plant. If your trees have 10 branches, don't take off more than 3. Removing a larger volume can stress the trees and send them into decline. In their youth they'll need all the foliage they can produce for photosynthesis.
Best wishes with your new redwoods.
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