When do you want to use them? If you have room to store them and time just let them hang out for about a year then cut to size. Depending on the diameter, splitting them down the middle long-wise will help them dry a little faster. If you are only interested in pen blank sizes, cutting down closer to pen size will help them dry faster still, but they may warp or check so don't go too close to finished size. Leave some extra just in case you need to true them up or cut off bad parts.
If you need them sooner, you can cut to pen size and dry in the microwave though that probably does not work for mass production. You can also use some of the techniques turners use for turning green bowls like soaking in alcohol or soapy water to speed up the drying. Lots of information on youtube. Just search "turning green wood" or "turning green bowls" or some variation.
