In most cases, the standard methods for assigning staff to tasks should suffice:

In cases where you find yourself needing to bulk assign teams across many different projects and tasks, that can be done through the bulk team assignment page.

This functionality can be accessed via Administration > Teams > *Select the team to assign* > Bulk Assign Tasks:

This page will load the tasks for all active projects where the team is not already assigned to the task. To easily assign the team, simply select the checkboxes against the relevant tasks and click the Assign Teams to Tasks button: