All you need to care for your ManGrates is a grill brush and some type of fat or oil to create a protective seasoning. Items that can be used to season and seal the cast iron include non-stick cooking sprays (like PAM); a basting brush and vegetable or flax seed oil; a clean rag and vegetable shortening (such as Crisco); or lard.
Before grilling: Brush off ManGrates and apply oil evenly and thoroughly on all sides of the grates.
After grilling: Allow ManGrates to cool, brush clean, lubricate with non-stick spray, oil or shortening and close the grill lid.
Your ManGrates will season more and more over time; well-seasoned ManGrates naturally resist rust and create a virtually non-stick grilling surface (the oils/fats seep into the pores of raw iron, sealing it).