Baking soda and vinegar is my go to cleaning mix

Soak racks in bathtub in water and cascade

Dishwasher if you have one maybe

I've poured a bottle of ammonia in a large plastic garbage bag, put in my BBQ grate and let it soak overnight....this should work for oven racks, too. Let it lie on a flat place, like your driveway.

I use Dawn in hot water and scrub with aluminum foil

You will need a double layer of garbage bags big enough to seal around racks and either oven cleaner or ammonia. Place racks in inside garbage bag, spray them heavily with oven cleaner or use liquid ammonia (as poster Connie mentioned), seal inside bag then seal outside bag. Leave somewhere outside overnight. WEARING GLOVES, remove racks from bags, discard whatever cleaner remains and dispose of bags (don't reuse those bags). Give a scrub to any stubborn spots with balled up aluminum foil or coarse steel wool. Rinse well (I would do all this outside because of fumes and rinse with hose on driveway).

Get a copy of Helouise's original book on how to do chores the easy way (Helouise's helpful household hints). Got it when I got married back in the '60s and has helped me through many-a-crisis.

Soak in garbage bag with ammonia overnight. Take sealed bag to car wash. Remove from bag, use hand held sprayer to remove the stubborn bits. No scrubbing!

Use the no heat oven spray like Easy Off. Remove racks, place on newspaper outside, spray, let sit a while and then either use a scrubbie or hose down. If badly burned you will have to use a scrubbie.