As little water as possible Dan. Spray on the AG Engine and machine cleaner and agitate with a paint brush allow to dwell for a few mins, rinse of using a low pressure flow of cold water from a hose pipe using only as much water as you need to remove the degreaser.
Anything your worried about getting wet, cover with plastic bags and dont spray the hose at! For these parts and clean using some degreaser on a damp cloth rather than spraying it on.