I found a couple recipes online.
BASIC MIX
6 parts sphagnum peat moss or coir
1 part EACH perlite & vermiculite
Combine & water until moist, then add seeds.
SOIL-BASED MIX
1 part EACH peat moss OR mature compost
1 part EACH garden loam OR topsoil
1 part EACH clean builder's sand OR perlite
ENRICHED MIX
4 parts sphagnum peat moss
2 parts compost
1 part perlite
1 part vermiculite
