Rockwool is a nice clean media that has a perfect Air: Water ratio and comes in a ready to use cube format.
When hydrated, each cube has a consistent 80% Water 20% Air ratio which makes it an ideal media for hydroponics as it is difficult to overwater the cubes. This prevents seedling problems such as damping off.
To use this media simply unpack it from the box, fully saturate the cubes and then drain them off, place the cubes onto your propagating table, place the seed in the pre-punched hole provided on top of the cube, shower the cubes with water to wet the seeds and leave the system to irrigate by automated controller. Once the seedlings are at a reasonable size for transplanting simply separate the cubes and place them in the main growing system.