You can split out the boo with a large knife and a mallet.
I don't think you want to "temper" the boo until it has cured. I wouldn't use direct heat to dry it out. If they are in slats already put them in a sunny, dry spot. The sun will bleach out the green and help to dry it. You can store them under your bed and use your house as a drying box. This time of year is usually pretty dry in most places.
If you are gonna use the boo for backing strips there is no need to temper it. It is plenty strong in tension. If you want to use it for ballies, tempering is necessary to increase the compression strength.