John, I divide mine every 2-3 years with a ginzu knife.
I use 18" clay pots filled with a 50/50 mix of Miracle Grow Potting Soil,
and orchid bark chip mix. (both can be found at HD or Lowes)
I fill up the pots 1/2 way with the mix, then plop in the newly divided chunks of Cymbidiums
(I have 3 colors now, chartreuse, rusty-orange and rosy pink)
then toss in a half cup of Osmocote around the rootball,
pack in more potting mix up to within 1" of the top of the pot.
This year they will need to be repotted again since they are about to crack their pots.
This time I am planning on using those big coco fiber lined hanging wrought iron planters.
(found some NICE big ones at Costco that look like the ones below but square and chunkier)
This way I can mount epiphytic orchids all over the outside of the pots onto the coco fiber and conserve on 'pot' space.
And orchids love the air circulation of hanging coco fiber open air pots.
You can drench them every day and not have to worry about them rotting.