I had two jade plants that both got powdery mildew and were slowly dying. One was my mother-in-law's and the other one was my mother's so I didn't want to lose them completely.
I broke off the good pieces at the joints and removed any leaves that look infected. If all you can salvage is a big leaf that is fine too, as jade plant leaves can root too. I purchased cactus mix soil and filled up the new containers. Then I just poked the pieces into the soil, deep enough that they could stand up on their own.
They are both doing really well. Every once in awhile, a leaf will begin to show signs of not being healthy so I simply remove it, along with any leaves that have fallen off. It is important to remove any dead or dying leaves to keep the plant healthy.