Any county assessor may request special assistance from the department of revenue in the valuation of property which either (1) requires specialized knowledge not otherwise available to the assessor's staff, or (2) because of an inadequate staff, cannot be completed by the assessor within the time required by this chapter. After consideration of such request the department of revenue shall advise the assessor that such request is either approved or rejected in whole or in part. Upon approval of such request, the department of revenue may assist the assessor in the valuation of such property in such manner as the department of revenue, in its discretion, considers proper and adequate.