Allow the machine to coast done a bit, then feed the tap into the work. Keep one hand on the brake. When you reach desired depth, operate the brake. The tap should rise smoothly out of the hole. Works great, but takes some practice.
Most professional shops use tapping heads.
In my work, I sometimes have to tap hundreds of 2-56 holes. I have a tapping head for obvious reasons. Tapping heads offer several advantages over other methods. First, they do a good job of limiting torque, and can be adjusted over a fairly wide range. The spindle holding the tap is floated so as to help align the tap with the hole and prevent stress on the tap.