I often sprinkle coarse vermiculite under and over seeds that I direct-sow outside. It keeps them moist and aerated and prevents crusting
I cut a narraw trench a little deeper than I wnat the seeds to be sown.
I fill a 2-liter soda bottle with coarse vermiculite.
Then I shake/pour it in a thin, shallow line on the bottom of the trench, then smooth-firm it level.
I drop the seeds on top of that layer of vermiculite at whatever spacing.
Then I shake/pour the right depth of vermiculite over the seeds, making the trench level or very slightly below grade.
Then I firm it again, and mist the bed or sprinkle gently with a fine rose head.
