I've used oats as a base carrier for spring frost seeding for years. Been "drilling" (use my old 8300 JD drills right onto frozen ground) for good even seed distribution. Go out just as soon as I can... typically this time of year here in Minnesota. Prefer to wait until all the snow has pretty much melted, so "snowless" has been accomplished, and then go out onto frozen ground right after we get a nice 3-4" snow, and drill right into that... NO TILLAGE AT ALL. The melting snow will press the seed down firmly onto the soil surface and help to keep it moist... along with the normal spring rains. Typically I'll seed about a 20 way blend of stuff, but generally it'll be about 6 different grasses, maybe 6 different legumes, and 3-4 brassicas (cows LOVE kale). Prefer to have put some winter rye out the fall prior too as well. I blend everything together with an old grinder mixer (just use the mixer), and then put it right into the big seed box... call it my "Handy Dandy Seed Tender Blender".
What species you use will always be dependent on where you are located... and what your goals are... do you want perennial pasture from your seeding, or annuals... do you want the plants to provide you with N? Do you want to prevent soil erosion? Is this permanent pasture, or rotated farm fields? What crop will follow what you're putting down today? Etc.
