I have to admit I'm a slacker when it comes to cleaning my grills. I keep the grates brushed and dump out the ash, but the only other thing I occasionally do is scrape out any chunks of fused juice/fat/ash from the bottom. I like to think of the layer of dust on the outside as an extra protective coating.
Same here. I season all my grills heavily when I first get them, so all I usually do to clean off crud is use a $3 wallpaper scraper. I remove the grates and burner covers and give them a good brushing with a wire brush and Steven's grill scraper, check the burners, then scrape everything down to the bottom of the grill. Then it takes about a minute to suck up all the scraped bits with a Shop Vac, and then I give the whole thing a good wipe down with a paper towel or a clean shop rag (which then is used to light my burn barrels when needed).
Then all I do is heat up the grill to medium, brush it with oil, and let it cool down, and it's ready to go for the season. If I'm cooking a lot with sauces I'll repeat the process once a month or even more often.