You can do this by having your baby latch onto the breast that has the clogged duct and let them feed and feed until your breast is completely empty. A completely empty breast often feels saggy or deflated and has no lumps or hard spots. Once your breast feels empty continue to let your baby comfort suck (if they like) just to continue to that sucking pressure on your milk duct.
This works best when combined with breast massages while the baby is nursing.
Happy Pumping!