In the garbage cans I would use a handful or two of a slower dissolving pellet food, perhaps shrimp pellets or a carnivore wafer to last a few days. If you can dose daily you could use ammonia that is sold for cleaning. No perfumes, no surfactant, just pure ammonia. Add enough to test 5 ppm the first day, then test and add enough to test 3 ppm after that.
Running all the filters is optional. You could dump all the media from all the filters in the garbage can and just run one pump or power head. The bacteria need good circulation, high oxygen levels and good ammonia levels.
I would clean the tanks and filters before. Yes, used tank water is perfect for cleaning the filters, and for filling the garbage can.
I would not feed the fish.