How can pumping help me wean?
The Breastfeeding Expert

When you try to wean you’ll begin to offer baby less breast milk, and it’s normal for your breasts to become uncomfortably full (aka engorged). Each time this happens, pump — or hand express — just enough milk to ease the pressure. If you were to pump your breasts until they were empty, your supply would stick around (or might even increase), but if you pump tiny amounts of milk, you’ll signal your body to slow down production. You should notice a decrease in milk within a few days.

 I’m trying to stop breastfeeding, and my breasts are super-engorged. What can I do?
The Breastfeeding Expert

Weaning should always be done gradually. If your breasts are uncomfortable and engorged it means you’re going a little too quickly for your body. Use cold packs to take down some of the swelling, then either pump or nurse your baby to fully drain your breasts. Then try eliminating or stretching the time between feedings a bit more slowly, allowing your body a few days to adjust each time you eliminate a daily feeding or pumping session. Don’t simply try to “wait out” the pain. It is extremely important to relieve the pressure you experience by expressing a little milk (with your hands or with a pump) to help you avoid mastitis or a breast infection. You may have heard that pumping stimulates milk production, but rest assured that milk production is only stimulated if the breasts are drained consistently over several days — not by draining little extra milk here and there.