Seeds and cuttings do not need rich mixes and will make root in just sand mixed with grit, as soon as they have a root system they need a richer mix so they can make growth.
My own mix is one third compost, one third fine grit and one third washed sand, put the cuttings around the edge of the pot, I usually put in five and then water.
With some seed I use a quarter compost then three quarters fine grit and washed sand, as soon as the seedlings have two true leaves I pot on to a one third mix then later to half compost half sand and grit.
This is what experience tells me works and I would think MD will use similar, he covers his Herb cuttings turning the plastic bag each day I never cover having found it sometimes detrimental causing die off.
Hope this helps.
Frank.
