there is some info in the advanced forum at the shroomery under a thread with a title something about not using a pressure cooker, basically involving taking a jar of grains about 1/2 full and adding water until it is nearly full then putting a lid on and letting it ferment for a few days until the pH drops below 4...similar process to making sauerkraut using the natural yeasts and lactobacilli present on the grains
now apparently this will work with some oysters and kings but the pH is low so they grow more slowly
so it works but I suspect if you added some sterile gypsum to bump up the pH before inoculating that the results would be better
same can be done with straw, fermenting and inoculating with grain spawn
I read once about a study in asia I believe that added a single lactobacilli strain with good results, so there may be some harmony in there
em is pretty powerful stuff so it is hard to say how it will go for you, only one way to find out though
good luck and let us know how it goes