Putting wax just on the outside of a pickup may due some help but the whole pickup needs to have the wax permeate within all the fine cavities and air should be displaced by agitation when hot wax potting. When the pickup is dipped in wax, at first the wax will solidify till the pickups become heated within and the wax can fill the fine voids. Again there is a fine balance between proper potting and destroying your pickup. Again, let a qualified repairman do this.