If you need to use 2-4lbs of product per 1,000 sq ft you would add 2-4 lb of product to spreader, start with a medium setting, then apply product to a 20 x 50 ft area (1,000 sq ft). If you have product left, your setting is too low. If you run out of product, your setting is too high. Because of the many brands of spreaders available the Heritage manufacturer does not provide the exact spreader settings.
Irrigation after Heritage G Fungicide application will depend on what and where you are treating. Please refer to the product label for complete instructions on your target disease. Otherwise you would wait 24 hours to water in.