Purge the crabs by soaking in water for about 15 minutes. A garden hose and an ice chest full of crabs works best. Light the fire under the filled boil pot and add the liquid boil, salt, Pro Boil, pepper, and lemon juice. Squeeze the lemons and oranges into the water and add to pot. Bring to a boil and boil for about 10 minutes.

Put the onions, potatoes, and garlic in an onion sack; tie the top closed. Lower the sack into the boiling water and cook for 10 minutes. Carefully add the mushrooms, smoked sausage, and corn to the sack and boil for another 10 minutes. Remove the sack and set aside. 

Dump the crabs into the boiling water; stir when the water comes back to a boil and cook for 10 minutes, add the shrimp and cook for 1 minute, then turn off the fire. Add all the ice to the water and move it around; the goal is to cool the water down so the crabs stop cooking and start soaking up the seasoning. Stir every few minutes until the crabs sink a little. About 15 minutes after turning off the heat, start tasting. If they’re not to your liking yet, let them soak a little longer, tasting every few minutes. When they are seasoned to your liking, remove them from the pot. Dump everything onto a newspaper-lined table and stand back. Enjoy your boil.