My Muffin was a constant shedder--she shed for several months straight. The vet recommended adding flax seeds to her diet, which didn't really help. I have also heard of black oil sunflower seeds helping with a bad/long molt, but it didn't work for me either. What did help for me was switching her pellet. She's an adult and only gets 1 tablespoon of pellets a day, but she was getting only Oxbow Bunny Basics T, a timothy pellet. I switched that to half and half Oxbow BBT and Purina Hi-Fiber Lab diet, a high-fiber, good quality, alfalfa-based pellet. It seems to have worked. So, I'd try adding a couple of sunflower seeds to her diet first (1-2 daily), then try flax seeds if that doesn't work (1/2teaspoon daily), and then switch pellets if that doesn't work.
Also, of course, check for fur mites (look like dandruff) and fleas (put him on a white sheet and look for black things jumping off). I'd keep track of his weight as well in case he might have an intestinal parasite--they can also cause weight loss and poor coat condition.
