Canna-oil is pretty easy to make, just takes a while. Get a crockpot with a low setting, dump a quarter ounce of good buds in it (chop 'em up), put a little more than half a cup of canola oil in there too (so you get enough oil for one pan of brownies), then cook on low for 8 hours or so stirring as vigorously and often as you feel up to, then strain the plant matter out and tada, amber-colored oil.

Wherever the brownie recipe asks for butter, just use that oil instead. Add a bit of butter too (but not much) for a little of the butter flavor.

That recipe scales up fine too, quantity-wise. I usually use 2.5 ounces of good buds, and a 48 fluid ounce bottle of canola oil, and that gives me enough for 11-ish family-sized pans of brownies.