Any county electing in accordance with section 273.052 is authorized and empowered to appropriate sufficient money to defray the expenses of making a proper assessment of all property in such county for the purpose of general taxation. The county board shall by resolution authorize the county assessor to employ such additional deputies, clerks, field workers, appraisers, and employees as it may deem necessary for the proper performance of the duties of the office of county assessor; such expenditure to include the hiring of experts in property valuation for any period deemed necessary, the payment of the transportation expense of such experts or other employees in traveling from place to place in the county, and generally any expense reasonably and directly tending to the procurement of a fair and true assessment of property within such county; but all such shall be made under the supervision of, and with the consent of, the county assessor.