If you end up with a "wet eczema" area then Epsom salts are excellent - dabbing it on with cotton wool (soaked in soloution from a bowl) is more effective than putting the foot in the solution. The trick to this treatment is to incorporate into your usual grooming routine (worth training for this even if you use an outside groomer). Train your dogs to stand, turn, sit, allow foot, ear, eye, teeth and gums inspections on a daily basis. Generally, soft brush the hair against growth, then comb with hair growth, brush with hair growth (include the tail on all these) and inspect each foot (include nails and use nail clippers every day, near the nail, so the dog get used to the sensation and the noise). Once you have an idea of what is "normal" for the dog it makes it easier to ignore the attention seeking. If you do notice that the licking has caused a lesion then a quick run through of the grooming routine, adding in the treatment with Epsom Salts, will not seem, to the dog, like attention for the licking. It does not matter how many times each day this treatment is given as long as the grooming routine is followed.
If the licking is habitual or allergic reaction - following this method of treatment reduces stress, strengthens bonding and reinforces status. Staus is reinforced because you have to be encouraging to teach the movement required, calm at all times - even when it goes wrong! - the dog is only rewarded physically when it gets it right and it is a very relaxing and rewarding activity for you both when it all comes together.