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When I clean my grates I use white vinegar. Sometimes MES a bit of lemon juice added. Place it in the smoker in a heat safe bowl. Fire up the smoker and let the vinegar boil for 15-30 minutes. Let it cool down wipe clean.
If you are talking removable items, if you must clean them, sometimes they must, take it to the drive in car wash and in the truck stall you'll find a hot steamer brush normally. Its not as good as a steam jenny but works almost as well. The immediately re-cure the grate.