Any utensil which is to be kashered should not be used for a period of 24 hours between the cleansing and the actual kashering by immersion. They re kosher. Immerse them in water for 72 hours, changing the water every 24 hours. Utensils used for baking during the year should be put away for the holiday. Chinaware, enamelware, earthenware, porcelain and plastic cannot be kashered 5.
Some people also cover the shelves with foil.
Ovens can be kashered by a thorough scrubbing and cleaning. Microwaves may be kashered by a thorough scrubbing then placing a glass of water in the oven and running it on high for a few minutes until the cavity fills with steam and the water disappears. A microwave that has a browning element cannot be kashered. Dishwashers may be kashered by scouring, not using it for 24 hours, then running it through a full cycle. Toaster ovens are a real pain to properly clean so just put it away for the holiday if you can.