I have some patches of bare earth in my back yard where the grass just will not grow. I figured I'd give a go at seeding it for moss, since I've heard that it works better for some poor soil conditions. My immediate problem is that the moss seeds are absolutely tiny, like the size of sesame seeds. The packet claims that the 1000 seeds are good for about 500 square feet, but short of carefully picking up and placing the seeds, I feel like they're just going to fall in clumps that barely cover a dozen square feet. Is there a trick to it? A good tool to use? I have a spreader, but even that seems to put down seed at a much higher density.
I have never used moss seed. I think vegetative propagation would be more reliable . If you could find some mosses in a local wooded area and transplant it. I have found it grows slowly but consistently. I have a small pond with a flagstone area where I put in some and it has grown very well . I would hand broadcast the seed , that is what I do with annual rye and fertilizer. For small seed you can mix the seed with something like sand to make it easier to handle and help to see where it is being broadcast.
As you realized, trying to sow individual tiny seeds 6 inches apart, outdoors, won't work.
You are supposed to sow them into seed trays and then transplant the moss plants after they have germinated. That is still going to be a lot of tedious work, but at least it is possible.
As blacksmith37's answer says, unless you really want some particular species of moss, just finding some moss that is already growing and transplanting it would be easier.
Just regularly spot treat any "normal" green plants (grass, weeds, etc) that appear with Roundup. Nature abhors a vacuum. Given time, assuming the habitat is suitable and with a bit of luck, more "primitive" plants (that Roundup doesn't affect) such as mosses, liverworts and ferns will naturally colonise the area. The advantage of this method is that you will end up with those species that are native to your location.