It begins with a tray...
mostly, its a survival of the fittest when i do it like this. which ever seedling is the first to pop or most vigorous, is the one that lives. i am keeping a few of the twins though, because someone in the area needs some. i just gently tease apart the roots, and transplant into another container. if youre careful, its not that hard
My recipes change with every passing year and with what ever resources I have available at the time. Whether it be locally sourced composts, manures, loams, soils, how well I did with my own composting over the winter, or what deals I happen to stumble upon out there in the "markets", I chose whatever is most economical and self sustainable. Recycling and composting old soils from the previous season counts for the bulk of my mediums in containers. Its very easy to create a living soil food web this way, rather than buying freshly manufactured mediums in new bags and then trying to bring them to life. I do buy a bale of peat, verm, and perlite now and again to keep adding to the pile or to create sterile seed starting mixes.
You can just about use any ingredient you want so long as you stick to a rough ratio of 50% compost, 30%% Loam, 20% aerators. This creates a nice, airy mix that also retains moisture optimally.
I would probably set "known" infected soils into a seperate quarantine pile for at least two seasons. Or stleast put them into the center of a highly active decomposition pile. A big pile of mixed wood mulch, chipped, gets quite hot in the center. Hell when I get done brewing, my piles f spent grain get so hot that I've burnded my self reaching into one! lol