Both the barefooted and the shod people, at least once a day normally wash their feet.
While most of the time, soap and water would do the trick, every so often you do need to scrub a bit deeper, and get some dead skin off.
Out of all the ways I searched on cleaning feet, this one is coming from a doctor, and is the simplest but best way to do just that.
Here it is:
Scrub Your Feet Clean
Proper cleansing of your feet will provide increased comfort, decrease foot odor, and will reduce the chance of infection, including fungus infection (onychomycosis).
When people shower, they usually spend a good amount of time shampooing and conditioning hair, and applying a variety of soaps and solutions to the body. However, because the feet are often difficult to reach and the shower floor is slippery, they often only get the soapy water that rinses down from the body.
There is a household kitchen cleanser, called Soft Scrub with Bleach, that can be effectively used on the foot. This product is available at grocery stores. Put Soft Scrub with Bleach in a small pump container and leave it in the shower. Pump some of the cleanser onto a small brush and scrub all areas of your foot a few times per week, especially around the toes and toe nails. The abrasive particles in the Soft Scrub will help to remove dead skin and bacteria. The chlorine bleach is effective against bacteria and superficial fungus that can cause athletes foot and thickened fungal toenails. Chlorine is also an effective deodorizer for the foot.
I tried it, and it worked for me.