I switched to DME for priming I think at batch number three ot maybe four just cause the dextrose isn't Rheinheitsgebot and it was easier then making gyle or going all grain.
I use 1 cup DME in about a quart of water at room temp, heat up to ~180°F, the DME should be dissolved, put a lid on the pan and let it cool down to 100°F or so over on an unused burner. Takes a little while, but you get good pasteurization after 20 odd minutes at 170 and you are waiting for ~100, maybe 120°.
I put that quart into the priming bucket with the first inch or so of a five gallon beer batch, don't sweat a little oxygen. Youa ren't trying to aerate, but don't have a cow man. Put some kind of loose fitting lid on the bottling bucket and go play a round of golf. Then bottle.
Then wait one month and put one bottle in the fridge for 24 hours, like that one bottle a week after the first month until it is ready. You'll have some carbonation at 2 weeks, but no, not yet. At one week, no, not yet. You'll have good beer in another 3-5 weeks.
I can't taste the difference, but it sure feels good to say Rheinheitsgebot.