Before cleaning your barbecue or smoker, you should check the Manufacturers Manual for cleaning recommendations and safety tips, especially when dealing with gas grills.
Cleaning a grill or smoker is no fun. Ok, now that we agree and have gotten that out of the way, let's see why it's important to do it anyway. Then we can examine how to do it as painlessly as possible.
Most food will expel grease and carbonize to some degree in a barbecue or smoker. Fats drip into the pan, smoke rises from the surface. The result? A black, crusty compound gets deposited on the interior. That compound is mostly carbon, with some unburned grease thrown in just to make the clean up that much more difficult.
Cleaning in layers will help make the job easier. Some grease can be eliminated when scraping the carbon off, but for the most part it will need to come off first. Fortunately, with modern oven cleaning sprays that's very easy to do - especially on a barbecue where you have easier access.
After allowing the barbecue to cool to just above room temperature, spray generously and wait at least two hours. Allowing it to sit overnight is warranted if you haven't kept up on cleaning.
Take apart any removable sections from the grill like grill bars, drip pans and lid. Always scrape away from you and keep a firm grip. Many edges on a barbecue are sharp and solid enough to cause considerable harm if your hand slips.
There's always a temptation to clean right away - both to 'get it over with' and because some things come off easier when the grill is still hot. That's true to an extent. Bonds between the material and the grill solidify when as the materials cool down. And a little scraping right away with a special scraping tool is okay in order to remove the large chunks of carbon from the grill or barbecue edges.
But wire brushing and other activities such as spraying with cleaner and wiping are dangerous when the grill is still hot. There's the obvious risk of a bad burn by touching the metal. But beyond that, a wire whisk will fling specks of hot carbon onto your arms and face. Bad news. Cleaning liquids that come into contact with hot metal will vaporize, often producing toxic gases. Another bad idea. Waiting may make clean up a little harder, but it's much safer.
A few hours later or the next day, you can wipe off the oven cleaner and grease deposits. These sprays work extremely well. But be sure to use lots of water, rinsing a sponge or towel frequently. You don't want any of the oven spray/grease residue left inside the barbecue. If it dries and remains, it will definitely impart a foul odor and taste the next time you cook.
Now comes the hard part: removing the remaining carbon build up. Here there's no safe alternative to elbow grease. A proper scraper will help, but even with it you will have to exert some force. Keep a firm grip.
Clean the barbecue regularly and each clean up will be easier than if the job is only done every third time or once a season. Your food will taste better and you'll get much less cool grease on your face and in your hair.