Maurice,
Depending on what wood it is and in what direction you cut it, ie with the grain or cross cut at an angle to the grain, you will want to cut oversize to your desired pen blank size as it will warp and twist. The amount it will twist will depend on species, whether it is branch wood or trunk wood and its distance from the pith. Wood will, generally shrink around 6-12%% tangentially, 3-6% radially and around 1% along its length. Its often better to cut boards from the tree rather than pen blank spindles as you will retain some of the shape better, but it will take longer to dry. Some woods will tolerate being made into pens wet, Olive for instance is rarely dry, for two reasons, firstly it is very hard to dry and secondly, the Italians in particular have no idea on how to run a country, fight wars or dry wood. Most of the stuff is sopping wet. Turn oak wet and you will end up with a load of matchsticks semi glued to a tube though.
When you do cut wood into thin boards or into pen blanks size spindles you remove a lot of the opportunity for the wood to shrink and build up the stresses which lead to the cracks. I wouldn't bother waxing pen blanks, if they are in danger of splitting through stress build up when they are that size I would rather they did it before I went to the trouble of drilling and putting a tube in it!
When you dry wood one of the most important things to consider is the tempreature and humidity gradient across the drying wood. The steeper the gradient the more stress that will build up as the wood dries, and the greater will be the certainty that it will split. The smaller the section that you are drying the less the opportunity to create a gradient of any significance.
Ive cut Laburnum, alledgedly a difficult wood to dry (no more difficult than any other in my opinion ), into small sections and put it in the oven at a savage 150 for four hours, but if you do this leave it in the oven to go cold. Has worked a treat and Ive never had any problem with retrospective cracking.
Its important to understand why wood cracks or rather it is important to understand how the stresses build up and if you know that you can work around it and if you then appreciate when a wood is going to cup you can compensate for it. If you are going to cut oak for pen blanks and it is wet, always quarter cut it, you will then only have shrinkage at right angles to the grain and you wont get distortion. Cut it through and through and you'll end up with a piece so cupped it'll be worthless.
You can get moisture meters on the internet, they're not very good but for a tenner you cant complain. Most wood when cut is in excess of around 35%, but this does depend on the time of year. Incidentally if you want to cut natural edge blanks for bowls, make sure the wood was felled in the winter, ideally about March. The Cambium layer, that between the bark and the sapwood, is at its strongest in the winter, if felled in the summer theres more than an even chance that the bark will fly off when you turn it, and that's dangerous.
Anyway back to Pen Blanks. There is a guideline widely repeated that it takes a year per inch to dry wood, so a trunk 10 inches wide will take ten years to dry. Cobblers! Its exponential anyway and very much depends on the wood. I've got two fourteen inch diameter yew logs five foot long that I bought when they were eight years felled, and that was four years ago. I took a slice off one last year and the wet ring was clearly visible around four to five inches in. But yew is difficult if not impossible to dry. In days of old they used to tie the trunk to a tree root and throw it into a river to wash the sap out for a year and then dry it. Do you know why they used to tie it on to a tree root?
Yup, otherwise it would have floated away!!
Anyway, a bit off the subject of drying pen blanks but quarter cut the tree and stick it in the oven, my oven stills smells of mulberry, but the wife hasn't a clue what caused the smell!