You should only ever have to log the details of your bookings once. Once the information is logged, specialist software such as Overture can generate emails to communicate all of the details to anyone who needs it: promoters, venues, tour managers, other agents, artistes, etc etc.
In addition to this you can allow any of these people to log in and collect any information relevant to them – information about bookings they’re involved with, plus any contracts and invoices they need. Agents can forget about the day to day admin and get on with the important stuff.