I need help with animals... well, a donkey. Farmer people, feel free to jump in.?

I have a farm. Nothing big, a bunch of chickens, some goats, a couple of cows, and some dogs. My uncle recently gave me a donkey that he got from some of his friends. He was given to me because my uncle doesn't have the time to take care of him, and school's out now, so I do. His hooves are filthy and grown in and under, his fur is ratty and clumpy. I know how to care for him physically, but the people who originally had him abused him badly. When my uncle got him, his bridle had been so tight that there were deep cuts from them pulling him with the lead rope. How can I get Dusty to trust me? I'm a good person and I love animals, but I just don't know what to do. Please help me.