To begin, make sure you realize that there is a difference in the material of silver doubloons and coloured plastic doubloons, and therefore, the cleaning procedure for both types will also differ. The silver variety need stronger, more thorough cleaning, whereas the plastic ones require nothing more than some gentle brushing with regular detergent or soap.
If you have the coloured, plastic doubloons on hand, take a small glass bowl, and fill it with warm water. Pour in a teaspoon of mild liquid dishwashing soap and mix it into the water, until it becomes frothy and soapy.
Now, use a small cotton washcloth to wipe all the plastic doubloons, and get rid of the loose dirt, dust, and debris they must be covered with. Then, tip the plastic doubloons into the bowl of soapy water, and let them sit for a minute or two. Once 3-4 minutes have elapsed, start picking individual doubloons out of the water, and use a baby toothbrush to scrub the stubborn dirt out of all the crevices and ridges in the doubloons.
Finally, lay the doubloons out onto a cotton towel, and allow them to dry completely – however, do not put them out in the sun, as this will cause the colour to fade. Once they are dry, you can use or store them.
However, if your Mardi Gras doubloons are silver, you will need to fill a bowl with ammonia, and soak the doubloons in this for 24 hours. Then, take them out, rinse them with cold water, and polish them with your preferred silver polish. Finally, allow them to air dry completely before using or storing them.