Start with a 20-quart pot filled over 1/3 with fresh cold water. In the pot add crab boil mix to the water. Squeeze juice from 2 of the lemon quarters into the water, and drop in the rinds. Add the garlic cloves, red and green pepper slices, mushrooms, scallions, whole onions, and hot sauce into the water. Bring to a boil, and then add sausage and potatoes. Bring to a second boil, and continue cooking for 5 to 10 minutes, or until potatoes start to get soft. Add the corn, chopped garlic, and start a count of 5 minutes. Do not wait until water boils. At 5 minutes, add mussels. 3 minutes later, add shrimp. Boil for 2 1/2 to 3 minutes. Drain immediately.
Serve with plenty of napkins.