Getting the filling into stuffed shells or manicotti can be a challenge. Using a heavy-duty zip-top plastic bag as a pastry bag makes it easier. Simply spoon the filling into the plastic bag, squeeze out the air, snop a 1-inch hole in one corner of the bag, and pipe the filling into the shells. Snip a small hole to start with; you can always make it bigger.
Try this Kitchen Shortcut with Four-Cheese Stuffed Shells with Smokey Marinara.