I can't speak for anyone else but for me the only time I'll collect CA junipers is during a rainy winter between Nov. and March but it has to be a wet winter. That means I haven't dug in a few years. Then 99.9% of my trees come from north facing slopes- the trees have a little easier time. I keep them usually in 100% pumice in a green house with high humidity for about 6 months then introduce them to full sun gradually over the first year. Then they get watered, fertilized and thats it for at least 3 years after collection. After 3 years when I see lots of new shoots extending then I'll think about styling.
There is a lot more too it but these are the basics. There are some good videos on collecting techniques on YouTube by Andy Smith.