Shake, strain, rock. Fine strain if you must.
Grapefruit cordial: for reference, see Paloma (Fully Loaded), but this is slightly simplified. Add peel of one pink grapefruit to jar, bury it in 3/4 cup of sugar and refrigerate for one day. Add juice of 1 pink grapefruit juice and half a lime, 2 oz. water, 1/2 tbsp. salt. Shake repeatedly until sugar totally dissolved, then remove peel and refrigerate.
I wanted to make one of my favorites, the Fully Loaded Paloma, so I had to make the grapefruit cordial and made it a bit more syrupy, so I decided to make something rum-based, as I love anything with grapefruit and Donn's mix works so well with rum. The bourbon just rounded it all out.