Bring cherry juice and sugar to a boil in a medium saucepan; cook, stirring constantly, until sugar dissolves, about 3 minutes. Remove from hit and pour into glass, refrigerate, to let cool. This can be done up to a week ahead of time.

Just before serving, add 1/2 of your cherry simple syrup, frozen cherries, wine, and salt to blender. Puree until smooth. Add 1 cup crushed ice and purée until smooth. Assess consistency, adding 1 cup of ice and blending until smooth, until desired thickness is achieved. I like mine to be slushy rather than milkshake like.

Assess sweetness. If you'd like it to be sweeter, add more cherry simple syrup and blend.

Divide among glasses and serve immediately.