Some of them won't let you TOUCH them during breeding, and some like you to hold the female. Poor little Wrangler (my mentors male that studded Brooke's litter) won't do it until you hold her, he's a funny little guy.
Once they get started it's only a matter of seconds before the actual tie happens, then they can be tied for anywhere from 5 mins to an hour. There's one Shih Tzu that my mentor has that ties for almost an hour...it's exhausting to WATCH!