I reckon its worth having a go with a cutting: its free! I take the point about a tree on its own roots getting a bit big, but my feeling is that cutting grown trees often have a different root structure than seedlings, which is less vigorous.
I would try: taking 10 cuttings about 20 cm long in late autumn/early winter. This means if 60% fail you will still get something. Get your 20cm pot ready with 2-3 cm of potting mix at the bottom, then fill up with propagating sand. Cut the end of each cutting on the diagonal. This exposes more tissue to the stimulation of the hormone powder. Dip in hormone powder and insert in the sand but make sure its not so deep that the end is in the potting mix.
All cuttings are a race between rooting and rotting (I think Christopher LLoyd said this?) Get 4 sticks (height of pot plus 3 cm more than your cuttings stick up) or two hoops of thin wire and insert them in the pot around the edge - this makes the supports for a plastic bag "hat". Cut the corners out (a big cut not a weeny one!) and put the hat over your cuttings. This creates a controlled environment, with some air circulation, where the tender shoots of the damson will have a little more humidity and therefore not suck to hard on the just-forming roots for moisture. I leave this sort of cutting outside and not in full sun, rather than on a windowsill (too much moisture stress). I water as much as I think it needs to keep moist, but not so much its swimming and starts rotting.
Do put a label in the pot so you know what it is later!
And the big trick is do not, no matter how tempting it may be, DO NOT pot up the cuttings until you see roots coming out the bottom of the pot. Often dormant plants (gooseberries are a classic for this) will create lots of leaves/shoots which makes you think that plants have rooted. The only real test, without pulling up a cuttings and ripping of what roots it does have in the process, is to watch for roots coming out.
Any why the wee layer of potting mix? Well I dont always get on to potting things up when I should, so it gives the cuttings a little bit of food, and a bit of moisture retention, until I do get my act together.
Good luck! - Pip