I generally keep the fine kind to sprinkle over mix when seed starting, and the coarse kind for amending potting mix. I've used the coarse kind in the past for seed starting in the closed container, and had good results. In my most recent attempt I inadvertently grabbed the fine stuff to germinate echinacea in a closed container. I currently have some echinacea sprouting in there, and a few have a first true leaf and are ready to prick out. Some of the smaller ones look like they're rotting. I don't think many are going to make it, especially if I don't pot them up soon.
Overall, I've had better results with the more coarse grade.
Karen