No need to scrub, put the oven rack in a bag: it looks like new again.

Next, you will need a bowl in which to place the tablet or detergent. In the bowl, to pour directly onto the tablet, you will put hot water so that the contents dissolve well. The water should not be too hot, otherwise you could puncture the bag. If the tablet has not dissolved completely, you can use a fork to speed up the process.

You will need to add 3 or 4 tablespoons of baking soda to the mixture. Thus, we will create a very powerful combination that will be able to remove even the most stubborn grease. The liquid should be poured into the bag. You have to make sure that it is not too thick and that the bag does not get punctured.

oven
At this point, the bag must be tightly closed so that the liquid does not accidentally leak out. Then place the bag with the rack inside on a flat surface. The oven rack, in the bag, will need to rest for about two hours. If it is very dirty, extend the time, e.g. let it sit overnight.
When the necessary time has elapsed, remove the oven rack from the bag and rinse it under running water. No scrubbing is necessary. It will be as good as new and ready to use again.