I'm no where near an expert on this subject and you can take my post with a grain of salt, but I rarely worry about how green a piece of wood may or may not be... I very rarely buy a bowl blank commercially, most of my woods are gimme's that someone has cut and allowed me to have a log or two in exchange for a bowl.... much of it is very green when cut. I have far more problems with warp than with check or cracking. I turn most bowls to size or very near to size and if I feel it needs further processing before I finish it, I have a 5 gallon bucket of denatured alcohol that I'll soak a piece in, or I have an old Hotpoint microwave in my shop that I can put a 13 inch bowl in and nuke it for a bit.... if I use the DNA, I'll let it soak for 1-3 days, then pack it away in a brown paper bag for a couple of weeks, then finish it... with the microwave, I start with a simmer setting, run it 2-3 minutes, cool for 20-30 minutes, repeat, and repeat... then I may change to a higher setting on the oven, then run it 3-4 minutes, cool for 20-30 minutes and repeat until I am satisfied... until very recently, I used a scale to check between nukings, or an estimate of how dry it felt... I bought a moisture meter for my Christmas and will be using that to get a better/hopefully more accurate reading. I tend to use the microwave more than the alcohol bath.
I rarely turn pens any more, but the woods on the tubes are so thin that for the most part they will dry rather quickly without worrying about cracking... some woods will crack no matter how dry they are... wood and brass expand at different rates of expansion and if the brass expands more than the wood, you have a crack.
