If you’re going to try this, be careful to tie the bag extra tight so no ammonia can escape, and make sure to put the bin outside to avoid any damage caused by the fumes.
The next day, open the bin bag in a well ventilated area and spray the racks down with a hose. Watch the cooked-on grease dissolve right off the racks, leaving them good as new.
If you’re using this method, take necessary precautions to avoid inhaling the fumes out of the bag, and use safety goggles and gloves.
Dishwasher soap bath
For this method, all you’re going to need is a bathtub, dishwasher powder, old towels and a few old sponges.
source: express.co.uk