Attila, what happeed to your little redwoods? I realize Southern California isn't the best climate for them, but I suppose you could create conditions for growing redwoods. I would guess that heavy shade cloth with little or no direct sun coming through. Even here, with the often cool and foggy climate, I keep my redwoods in mostly shade. And plenty of water.
Re. foliage. Redwoods will get very compact after a few years of pinching, feeding, and more and more pinching. The one I posted was a scraggly little thing when I bought it.
I pruned them too much, too late in the season, and left them in the scorching sun.
For starter, how do you exactly pinch the foliage, and when. I imagine the pinching off the leaves doesn't do much - but it may stimulate new branches....I have no idea.
So the young branches must be pinched - but when? A new shoot may be pinched when 1 or 2 inches long (very young and not yet lignified), or when it starts lignifying? Again, I have no idea.
I think you can start pinching anytime the branch is the length you want, and it doesn't matter if it's hardened off or not. I made a couple of before and after images by merging photos.
Bob and Zack Shimon should write a book on Redwood Bonsai. They are the experts. Another local expert and friend/fellow club member is Tim Kong of San Francisco.