Contrary to popular belief, manure used as a substrate for mushroom cultivation does not smell. At all. In fact, if there is even a faint smell, it's sweet, kind of like fruit. Ideally, it shouldn't smell like anything but the mycelium growing in it. Only dried manure is collected, and it is pasteurized to the point of fractional sterilization. It's the bacteria present in decomposing poo that makes it smell... Hence, no bacteria, no smell.
And, BigBudEddie, I'd recommend against innoculating manure if this is your first grow. Not that it couldn't work, but you're likely to fail. Sterilization (of absolutely everything) is key. Infection causes a lot of inexperienced and ambitious growers to fail, and if you're working with shit as your primary substrate when you're beginning, it's much more likely to become infected if you haven't perfected your technique. Once you get a little practice, growing mushies is beyond simple, but you need to develop good practices. Manure does drastically increase potency though, and mycelium loves it. I would recommend you start with some variation of the PF-Tek using jars. Starting with a grain substrate. Brown Rice Flour is what most people start with as a substrate, and it's good. You can also use Wild Bird Seed (which helps with potency). I've used popcorn with a lot of success, and it's probably one of the most favoured substrates as far as ease of use, availability, and potency. And yes, I'm talking about the popcorn you buy in the store... Not microwave, mind you, but the bags you get for air poppers.
If you do want to try your hand with horse or cow shit, grow the jars using a grain substrate first. Then spawn to manure for a bulk grow. You'll build up a bit of practice working with mycelium, dealing with the drama of troubleshooting infection, and when you do spawn it into the manure substrate, well.... you'll get a shit ton out of it. No pun intended. If you're dead set on using it as your initial substrate, I recommend you get it pre-sterlized in a substrate bag. There are a lot of suppliers who sell these... They're quite easy to use. It's sealed, and usually comes with a self-healing innoculation point and filter (the mycelium needs air for continuous rhizomorphic growth). After you innoculate it, you just put it in a warm, dark place and forget about it until it's done. Basically the same idea with jars, but with them you need to check for foreign bacterial and fungal infections regularly.
If you need any help, let me know. I've been there, done that.
~Will
