OK, I've had a ton of blocked ducts, and am getting to be a real pro at getting rid of them. I've tried lots of tricks, but two of them in conjunction work the best:
1. Take an advil an hour or two before your next pump/feeding. Its anti-inflammatory properties help the clog get out, plus pain killer - yay.
2. Put a hot compress on the spot for a good 20 minutes right before feeding/pumping. Longer if possible. This thins out the fat in the milk and further expands tissues.
Massage gently while feeding/pumping. No more clog.
Most of the crunchy advice skips the Advil part. I think that's why I read so many complaints of it taking several feedings for it to go away. I would take hot showers, pump leaning way over, massage the thing as hard as I could stand it and it would still take a day or two for it to go away. I think the Advil is critical, but of course, that's a drug. Of course, you let these things go long enough they can develop into mastitis, and that's antibiotics. Luckily, I've not had to deal with mastitis yet... knock on wood.
So there you go - anti-inflammatories for clogged ducts.