The rickey is approximately 1 part tequila, 2 parts simple syrup, 2 parts fresh lime juice and 3 parts ice. Blend in a blender. Then add twice that amount of light beer to the slushy margarita.
Basically, for the Rickey, you just need to get the frozen margarita right, and then it’s 2 parts dos equis to 1 part of the margarita.