Step 1: Separate her from the others and ask her to stand on a mat (providing you've already taught this, it's a good place to do stationary work.
Step 2: Working at liberty, begin by tapping the side of her neck - click/ treat for standing quietly
Step 3: Gradually increase pressure of tapping - click/ treat for standing quietly
Step 4: Poke her neck, click treat for standing quietly and gradually increase strength of the poke
Step 5: Use the tip of a ball point pen to press into her neck, being careful not to press deeply enough to hurt her!
Step 6: Instead of poking, now pinch her neck.
note: If she walks away, that's okay! Ask her to return and back up the training, i.e. decrease the pressure of tapping/ poking and build it up again. Reinforce her often for standing quietly.
I asked Dorica to be brave and stoic - after all, she is a donkey!
Two years ago, this worked well - by the time she needed her Tetanus shot, she stood quietly for the vet and this resulted in far less stress and zero swelling or hot spots after the injection. But this winter, she had two IV injections due to the impaction colic and now she is worried about shots again. So I have started working with her again to build her confidence before the vet comes this Sunday.
If I can get the vet to pinch her neck and click and treat her a few times, it should go well!