California Live Oak is difficult to say the least for me so far. Put it this way, the one I collected back in Feb. may be dead, and had some roots, and I was very careful. Some say they are easy to collect, but I have never had any success with an airlayer, cutting or a dig so far, we will see. People say airlayering is iffy and cuttings are a nogo and that has been my experience as well. Even the recent rootwork on the young tree I have been raising for a few years seemed to revolt into dormancy as the buds were popping. It seemed to tell me to just go $#@% off for trimming it's lankey roots back half way.
I'm probably timing it wrong and just need to figure it out, like you, trial and error.
Give it a try and try to remember the bud state each time when you attempt to airlayer or take a cutting and who knows.
I've had 100% success collecting both Coast and Interior live oaks so have never tried airlayering. A friend has tried for several years to layer a Cork oak and says it only seems to get more and more swollen at the layer site but no roots. I have an Oracle oak (Black oak X interior live oak hybrid) that I plan to try layering this year. We'll see...
I was able to successfully take an air layer off a Valley oak last year. They tend to need constant attention because they try to heal the wound and callouse over the gap. I used Black polypropelene plastic to retain the heat from the sun and noticed that the side that was facing the sun exposure actually had better rooting.
In all it took about six months from starting the layer to severing it from the parent tree. The layered section is recovering in the garden for a year and I plan to start shaping it next Spring.
I don't really know. I've dug oaks anywhere from January to April and even a few in the August to October. I always look for feeder roots and don't dig if they don't look promising. It's also important to completely defoliate the tree when you collect it. If the weather is dry I try to mist the trees several times a day.
Usually buds start to pop all over the trunk in a few weeks.
Hope this helps.
Heres a really good article at Harry's site on collecting/repotting oak. I have a scrub oak that I want to air layer but it sounds like they are stubborn so may have to pursue other options. I am going to try the repotting this year like this article points out to do.