Yes, this is pretty much exactly how I do it and I've tried a few different ways before. I use about an ounce of chopped bud with 1.5 sticks of butter (0.8 pound) - which is a bit less than Tokin' Black Guy (love the name) but I simmer it for 4-5 hours with maybe 4 cups of water. The budder floats to the top anyway when you cool and refrigerate, so I don't think a bit more water dilutes anything. This makes potent green budder for me - one choc chip cookie is enough to get a pleasant buzz - and three was suitable for seeing Roger Waters live
I don't reckon you need a pressure cooker or any special equipment, just a large stove top pot, lid and low temp for hours. Hope your cooking goes well