I have worked with them just a few times, introducing (and charging) the clicker, then presenting a target for them to touch with their noses. This is the first behaviour that we are asking them to do - touch the target.
I present the target, and after the donkey touches it with her nose, the target is removed and the reward is given. It's important to offer the food away from your body and if the donkey looks for the food or checks your pockets, you pretend to be a post! Stand still, don't back away and wait until she finds the reward in your outstretched hand.
It's a good idea to unfold your arm backwards toward the donkey so she takes a step or two back before getting the food. This way she learns that the food will not be right next to your body. It's so important to teach good food manners at the very beginning!
It has taken Rose and Heather a few lessons to make the connection that they are supposed to touch the blue ball but today they "got it!"