You can make really FINE screen from Fiberglas window screening and a large "embroidery hoop", I think they're called.
Window screening is usually around 24 mesh, so it can be used to clean medium-small seeds, or sieve soil and pass only medium-sand and fine-sand grains.
Sometimes with small seeds, I'll make a drill in the soil, then add a little medium vermiculite, drop some seeds, then add 1/4" or so of vermiculite on top of that. Firm down, water.
Usually I only bother with that if
- I think my clay soil is likely to form a crust,
- or I might not water every day,
- or I only have a few of those seeds yet don't want to start indoors,
- or I just feel like experimenting.
