In a very large pot heat 3 gallons of water until nearly boiling. Add dry and liquid crab boil, squeeze in lemons, then throw in potatoes, garlic and onions. Boil 10 minutes. Add everything else. Cover and boil 5 minutes. Turn off heat. Uncover, sprinkle in 1/4 cup salt and 1 tablespoon cayenne, stir it up, cover again and let sit for 10 minutes. Drain off liquid. Line table with newspaper and dig in.