Of course you can, if already in descent LVL CHG and trottles in idle (ARM), just disconnect autopilot and follow FD pitch bar. If in V/S you must disconnect autopilot, deselect SPEED and follow pitch bar. In both cases you can (must) manually operate the trottles as you wish and you can turn FD`s off on either side (FD bars will then disappear on that side).
As long as the thottles are armed you have alfa protection and they will engage if you press TOGA.