I use pine shavings bedding. I think maybe part of the problem is that I have been using sweet PDZ which is keeping it very dry.
I'd say both of these are contributing. I didn't get good composting either until I moved away from using so much pine shavings...wood takes a long time to decompose. When I started using leaves and other yard debris and mixing in green stuff from weeding the garden, canning waste, the occasional hay from cleaning out the nest boxes...basically a wider variety of particle sizes and composting rates on bedding materials....I started seeing more composting action.
I also stopped encouraging the birds to dig through the bedding under the roosts and I stopped trying to flip it too deeply too....I found that released too much moisture from the depths of the litter that I really needed for composting the materials under the surface.
Now I just flip the top layer lightly under or throw dry material from another area of the coop onto the nightly fecal deposits to cover them, trap their moisture and smell under the top layer of bedding, and to encourage bugs to come up and work on that manure...they won't do it when they can't hide under the bedding.
Ever since making those changes, I've not had a problem with it composting too slowly but rather too quickly most of the year....when that starts happening I'll finally throw a little pine shavings or wood chips in the deepest part under the roosts to slow down my composting a tad.
Right now is the perfect time to get away from wood shavings for bedding as there are free bags of leaves on nearly every corner in town. I'll be collecting truck loads for storing out here for winter and spring bedding.
I'd move away from the PDZ...it has no real purpose in composting litter as you want it to be a little moist under the top layer.