Place 5 limes and 1 orange–which should be at room temperature–on the counter and roll them with your hand, back and forth, while applying pressure. Be careful, you don’t want to break them open, do it semi-gently. They’ll feel like a sem-filled water balloon when ready. This way the citrus will yield more liquid when you juice them.
Juice the limes and the orange in a large measuring cup, then add in 1 cup of tequila, 1/2 cup of grand marnier, and simple syrup. Mix together.
Pour 1/3 cup of coarse salt into a shallow bowl. Using one of the juiced limes, swipe the outer rim of one of your glasses. Swivel the glass upside down in the salt until the rim is covered. Repeat for each glass.
Add a heaping cup of ice to the blender and just enough of the margarita mixture that the ice is not covered. Blend, adding more ice or margarita mix until the desired thickness is achieved.
Pour the frozen margarita into a salt-rimmed glass, pop open a Corona, and place it upside down in the glass, submerging it into the margarita. Repeat for each glass.
Now get that party started and enjoy!