I have used molasses in a few brews now.
If you are using just a couple ounces in secondary for flavor rounding, like in a Kotbusser, the grocery store stuff is fine, just pasteurize like you are making a mead with honey, 40 minutes at 140°F is great.
If you are using it as a chunk of your mash bill, like a Caribbean style export stout, go with a 90 minute boil and boil it hard while you are waiting to add your (60) hops. That extra 30 minutes of boiling cuts 2-4 months off "age until mellow."
Besides the previously mentioned, you can often find 82 Brix molasses in 28 pound jugs in the cattle feed section at your local farm and garden. Also outdoor outfitters like Cabellas during spring bear season, at least in states where it is legal to hunt black bears over bait.
Anyway, my house pale is about dialed in and I have been playing with a Carib style export stout for my second tap. Nutmeg and black pepper are keepers, don't bother using gunpowder in your pirate stout, tomorrow's headache won't be worth the amazing headrush.
If you must, sprinkle a little magnum pistol powder (like Hodgdon H-110) in some rum punch. You won't do it again, I promise.