Cooling by itself is not in itself the solution to cure heel spur/plantar fasciitis, but it is often advised combined with other treatments like physiotherapy. Coolong often works well for inflammations, as it stimulates the blood circulation. The technique is especially usefull in the early stages of a heelspur.
Cooling can be done using ice, packed in a towel, an icepack or alternatively a cold can of soda. Whatever you use, make sure not to expose the skin directly to frozen materials, as this can lead to frostbite.
To be most effective, repeat the cooling 3-4 times a day.