The board of supervisors of any county or the boards of several counties acting jointly may employ, upon such terms as they approve, any person competent therefor, except any member of a local legislative body or city or village official, to represent such county or counties in regard to the assessment of metallic mining properties including proceedings to review such assessments. Information furnished such employe in his official capacity shall be confidential and shall not be divulged by him except in accordance with judicial order or as required in the proper discharge of his duties.