The grill that sits on top of my little barbeque is cast iron. The surfaces
on the grill it are not very smooth, so its really difficult to clean off
the burnt on residue.

A stainless steel grill I also have (but dont use much, because it does not
sit well on the barbeque) is easy to clean, because I can soak it in a water
tank for a week or two after use so the burnt will always scrape off easily.

If I soaked the cast iron one like that I think it would quickly turn to
rust. So would anyone have any experience of easily cleaning a rough
surfaced cast iron grill after use? Thanks.