Please don't. Get a steer, or if your getting a bull to breed some cows, afterward steer him, give it some time then procede with great caution. Bulls are dangerous. And tame bulls are more dangerous. They can be gentle and easily managed. Until its time to breed. Then they only have one thing on their mind. They can smell and/or hear a cow in heat from many miles around. Bulls
should never be made friendly. They don't give one shit about their training, care giver, being respectful, even fences unless it's seriously bull proof..... they are big, strong, an potentially dangerous..... Get a steer. They are the ox. Don't mess with bull testosterone. Them giant things hanging down there produce a lot.
Better yet is take one of his bull calves, steer it young an raise to be you riding critter... Much safer, easier.