I load mine up in a black trash bag and spray it down with oven cleaner. Leave it outside in the hot sun all day then hose the grates off. Works like a charm.
I bought myself a big rubbermaid tub, fill it with hot water, simple green, and let those babies soak for a day or 3. When I take em out and wire brush em and hose em off they are clean as new. A little bleach water spray on em afterwards to get off any nasties as well.
The grates from my WSM just barely fit in my Weber gasser. I hit them with high heat for a few minutes, then brush them off. I just want to get the bulk of the gunk off, I don't care if they're spotless.
huh? clean what?, on a serious note, I sometimes being lazy just load them up with all the other parts in my oven, and do a self clean, it really works great, kinda expensive I"M SURE of it
On my grill dome i open the vents for an hour or so after i am cooking, the temp gets high enough to cremate anything off the grates. they wipe clean after that. I am starting to clean my bandera grates by laying them on a hot fore for a few minutes and brushing them off. I don't like the idea of using chemical cleaners on my cooking surfaces, but that's just my .02 worth.