I soak the rye grain in a five gallon bucket overnight. The next morning I rinse it to remove tannins, dust and nasties. Drain it and mix in gypsum to prevent caking during sterilization. I load it into filter patch autoclavable bags or glass canning jars with filter lids. I use an All American 941 outside on a turkey fryer. I can fit 18 quart jars or 6 bags. They are sterilized at 15PSI for: 2 hours for jars 4 hours for bags. They have to cool overnight. I use a liquid inoculum to introduce the mycelium into the bag with aseptic technique.
I have a special filter called a laminar flowhood. It gives me a clean, contaminant-free workspace. I make petri dishes with malt agar medium and inoculate with a mushroom culture. When the fungus has grown enough, a small amount of water is added to a special blender, sterilized and allowed to cool, then the culture is added. The blender only requires a couple seconds to create a slurry of mycelium. I dump the entire contents of the blender into a bag. I usually see mycelium growing on the rye within 12 hours and complete colonization of the mushroom spawn in 4-7 days.
You can also inoculate the sterilized rye bags with pure colonized mushroom spawn. I usually make 12 bags of MASTER spawn. I use 2 bags right away and put the other 10 bags in the fridge and whenever I need more spawn, I will grab a bag and use it to inoculate 12 new bags.
I started my own mushroom farm, which I operated alone from 04-07. I grew oyster mushrooms for restaurants and I was testing other varieties. The market got flooded with new growers like myself, prices crashed, consumers had little appreciation for freshness, and then the recession hit and the bottom dropped out. The gourmet mushroom market has recovered but prices are still low. Shiitakes and brown button mushrooms(bella, crimini, portobello) are no longer considered "exotic" by the industry insiders. I just saw oyster mushrooms at the local Marsh grocery store for $6.99/lb. In '06, I wouldn't even wholesale for under $9/lb. Edit: Not only were restaurants willing to pay $9/lb, they were also more than willing to pay for airmail to get the product at its freshest.
Try to purchase organic, American grown mushrooms whenever possible. Farms use a lot of insecticides. Mushrooms grown in Korea or Asia are shipped over on boats and are not fresh.