100% success using air-layers while trees are actively growing, and, when you have access to original tree.
Close to 100% success rooting current season, green, semi-lignified cuttings.... rooted in coconut coir....which I buy in compressed blocks, at the local pet stores.
I fill the bottom 2/3 of a 2-liter soda bottle with the barely damp, coconut coir, and I push a long 3/4" - 1" hole into it right down the middle, and as long as the stem of the cutting. I insert the cutting into this hole and firm the coir around the stem for good contact. The cutting has all the leaves cut off except the last two-three small leaves growing near the terminal bud. I then take another 2-liter soda bottle, cut off the top end with the cap, and place this cut bottle over the fresh green cutting, making a mini-greenhouse. I leave this set-up in a warm, very bright location...out of direct sun. Roots start showing within 3-4 weeks. Voila....new trees.
Have fun.
Frank
EDIT: Never tried rooting dormant wood...yet.