Guava Margarita With Tamarind Salt

["Make the Ice:

Place the extra juice in a small freezer-safe ziplock bag or container and freeze until icy (like sorbet). About an hour or so depending on your freezer.", "Salt the Rims:

Take a bit of the tamarind candy and carefully rub on the rims of your glasses. Some of the sticky brown stuff should be visible on the rims. Put some salt on a saucer and inverting the glasses, carefully press the rims unto the salt, working in sections. Put the glasses in the freezer for at least 15 minutes.", "Make the Margaritas:

In a cocktail shaker, mix the cup of juice with the orange juice, then add the tequila. Mix some of the icy juice (which should be the consistency of crushed ice, ideally) from the freezer, and shake well. Pour the mix into the chilled glasses, garnish with the lime or calamansi and serve immediately.", "Last things: Use guava juice, not nectar, which I find to be too thick. Just don't forget to shake the juice well in its box or bottle before using to make the ice and the margarita. I prefer the pale, greenish-yellow juice, although the pink one is pretty. You can put more of the guava ice into the glasses, and can water down the margarita with a cube or two of plain ice if you want. Use a metal mug if you don't have a cocktail shaker. And use whatever short glass you have if you don't have margarita glasses. And most importantly, don't skip the tamarind salt. The drink isn't the same without it. Salud!"]