Supply and Clogged Duct Problems Pumping

I've been almost exclusively pumping for the last month after returning to work in January. I work long 12+ hour days and my LO gets very upset at the slower flow after using bottles all day.

Lately, I've been having a recurring problem with painful clogged ducts and reduced supply. The reduction came, of course, just as LO is starting a growth spurt.

Does anyone have suggestions on how to resolve some of these issues while pumping?

What I've tried so far:

Warm compress

Massaging painful spots before and while pumping

Increased time spent pumping (to about 30 minutes for both sides every four hours, and imitating cluster feeding in the evenings).

These all seem to help in the short term, but the painful lumpy clogged ducts seem to come right back every day.