Last year (2013) and this year, Extension Service recommended a general 4-0-2 spread.

   Using 46-0-0 (Urea) that works out to about one bag for 10,000 square feet.  Use setting of about #12 on the     Scotts broadcast spreader.  The lawn is about 30,000 sq ft so three bags is about right.
   Using 60-0-0 (Potash) try one bag on a setting of about 10.