Good question!
Don't touch QWERTY for a couple of weeks if you can. Practice typing the alphabet for starters. Also, force yourself to type everything in Dvorak. When I took up Dvorak, I remember taking 5-10 minutes to write a 2-line email, but I didn't give up, kept doing it, and my speed got better and better.
If you can't handle the inevitable initial frustration of going all out with Dvorak, you can take it easy and make up a list of short words, say 20 words, that cover all letters. Type the first word a few times till you master it. Then the 2nd word. Then put the words together a few times. Repeat, slowly adding more words.