The next time you decide to spend the day at the beach, take advantage of the "on location foot treatment." Brazilians, particularly, are known for scrubbing their entire bodies, particularly the feet, deep into the sand while they relax on the beach.
When going to the beach, take a small vial of ingredients with you: 2 tablespoons of canola oil (or use your suntan oil!), and, a small vial of rosemary oil -- or premix and take one vial.
Once at the beach, use an empty container (a soda cup is fine) to mix the ingredients together. Mix into a paste. Massage sand scrub onto feet (and elbows), concentrating especially on problem areas. Rinse off in the foamy waves, pat dry with your beach towel.