A flush is when all your muchrooms grow in and stops producing more. That is your first flush. Once u pick them all and another set of muchrooms comes in, thats your second flush. It keeps going like that till they stop growing or u get contam. Between the flushes I'm pretty sure u r supposes to dunk and roll in vermiculite.
Agar is like gelatin but it isn't. U can get some agar agar off the internet. Boil potatos(4) in a qt of water till their soft. Filter it thru a sock into a container. Take a pint of potato water, put it in a pot. Mix in 2 or 3 tsp of honey and 9grams of agar.
Cook it for 5 minutes while stiring constantly till its all dissolved. Put mixture in a pt canning jar leaving an inch of space in the jar and put the lid on. Pressure cook it for 15 min, wait till its cool enough to hold the jar and pour into petri dishes u can order online.
Once they r cool u can put just a smidge of spores in the dishes and it will grow mycelium which you can use to knock up grain jars such as wild bird seed.
Wild bird seed jars. Poke a 1/4 hole in the lid of qt or pint canning jar lids and stuff with polly fill which is pillow stuffing. Get cheap bird seed and boil it for 1/2 an hour. Don't worry about rinsing it or anything, it dont matter. Once its boiled put in strainers till most of the water is gone. Fill your jars up, spin the modified lids on and put aluminum foil over the lids to keep water out while pressure cooking. Stick the jars in the pressure cooker, fill the cooker up with a couple inches of water and let it pressure cook for an hour and a half at 15psi.
Pull the jars out when done, let cool to room temp and knock up with half a petri dish of grown out agar or a couple cc of a spore syringe.
Once your jars are colonized or mostly anyway u can hydrate a 650g brick of coc coir from the pet store to field capacity. Stick it all in a big pot and cook on low for a half hour till all the coco coir is hot as fuck. Once its all hot pour it into a clean 66qt clear tote. If you have too much water you can add vermiculite till it just barely drips when squeezed (field capacity). Once everything is cooled down take 5qts worth of mycelium and break it up and mix it into the coco coir real nice. Crack the tote lid and put a cfl light by the tub. Spray it if it drys out.
Thats just one way to grow bulk.