Nick, An initial disclaimer: I am not a representative of the vendor nor the manufacturer of this product, nor obtain any compensation from them in any form.
I have used SoilGuard (Gliocladium virens.....aka, Trichoderma virens) quite successfully in preventing damping off when starting tomato and pepper seedlings indoors in the spring. The product listed here:
https://www.7springsfarm.com/products/soilgard-microbial-fungicide-5-lb-bag?variant=41621324169421&aa_source=google&aa_medium=cpc&aa_creative=554572136046&aa_campaign=15015030199&aa_content=127454790174&aa_placement=&gad_source=1&gclid=CjwKCAjw1920BhA3EiwAJT3lSeNJ3gVhCWWzoImqjmsKKoadZMUQX23CGcs2IpfZEsU6RLOD-HweGBoCJq8QAvD_BwE
would go a long ways to assisting with many diseases that may affect your beds, but I can't speak to how it may suppress late season diseases because I'm only using it to produce healthy seedlings for planting. Granted, the fungus in the product will tag along with the transplant and help to protect certain diseases in the garden, but (for example) we still get late-season Septoria on the tomatoes. So it's difficult to say how protective it would be against foliar diseases.
More to your question: I have found that a handful (~2-3 tablespoons?) of the product mixed in with damp potting soil/compost and kept moist for several days will produce a fair amount of mycelial growth (brown colored) across the top of the soil. By default, as a soil-dwelling fungus, I'm assuming the entire mass of potting soil/compost to be infused with the mycelium. This *usually* can be stored in a cool place for at least a year or two with little loss of viability. Just let the mass of soil and fungus dry down over a few days (no watering), then bag it up and place in a cool place like a
root cellar for storage. This will provide at least one leg of your disease control strategy and be provide ideas for culturing other suppressive agents for your garden.
A bit technical, but a good conceptual overview can be found here (appears to be open-access):
https://apsjournals.apsnet.org/doi/10.1094/PHYTO-09-22-0324-KD
Good luck!
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