I have used Pam to keep salmon from sticking to the grates. However, I've done this on the recommendation of others, so I don't really know if it's required. Other than this, I don't find the need to apply anything to keep other kinds of barbecue meat from sticking.
There is now a "Pam Grilling" spray, but I suspect it's just a repackaging of the same old product. If anyone has experience with it, please post about it. You could also apply olive oil or other cooking oil to the grates using a paper towel.
You would think that applying a non-stick cooking spray all over the grate would make it easier to clean afterward, but that doesn't seem to be the case. When I've prepared the salmon and sprayed the whole grate, the overspray on the areas where there's no meat just bakes onto the grate. It does not stay in liquid form and must be scrubbed off.
When it comes to how (or whether) to clean grates, that's a whole different issue and everyone has their own approach. I wash my grates using hot, soapy water after each use. I find that the sooner I get them into the water and let them soak for about 15 minutes, the easier they are to clean with one of those Scotch-Brite-type barbecue scrubbers.
In the past, I found that just brushing the grates with a brass bristle brush or aluminum foil did not get off all the "stuff" I wanted to remove. For a while I burned-off the grates using my gas grill or over the hot coals before I started a cook. The problem with that was that the high heat burned the nickel finish right off the grates, which allowed rust to set in. And if I left the greasy grates in the cooker for any period of time, it invited a lot of ants and other insects to make a home inside my cooker.
I know washing grates isn't for everyone, but my grates are now going on three years old, the finish still looks great, and there are no signs of rust. And to bring this back to your original question, I suspect that the presence of a good nickel finish helps keep foods from sticking and makes cleanup easier.
Regards,
Chris
[This message has been edited by Chris Allingham (edited 06-28-2001).]