Here is one tutorial https://www.hometalk.com/41536285/clean-oven-vents-in-minutes-with-this-easy-kitchen-hack
I put mine in the dishwasher. Soak in hot water and Dawn dish liquid.
put them in pan,glass casserole type dish cover with boiling water and Dawn Dish soap let soak then scrub gently rinse with boiling water to get grease out. If you put them in dishwasher they will turn gray from oxidation.
I just put mine on the top rack of my dishwasher. They come out sparkling!