You can do a little stabilizing of the pen blanks by soaking them in a 50/50 mixture of PVA glue and water. I leave them in the mixture until they start to sink. Then let them dry for a week.
Take your pick on the glue. Elmer's won't change the color of the wood, but it isn't as hard and it is more difficult to sand. Titebond and other yellow glues will be harder and easier to sand, but they will add a yellow color to the wood.
This takes some time, but it saves a lot of expensive CA glue. At the least, this will solidify the wood enough to get you down to round, and then you can start using the CA glue. Sometimes it will soak all the way through the end-grain of the wood and you will have a thoroughly stabilized pen blank.