Question re kashering my microwave for pesach

Question

Dear Rabbi, I checked your halacha page regarding koshering microwaves. You indicate as follows: "Microwave Ovens can be koshered by putting a bowl of water on the highest setting for twenty minutes." So, my question is, which bowl do I use to do this? One that is kosher for pesach that I have designated for pesach use or one that is from every day? My issue is if I put the KP bowl in, aren't I putting into a chametz microwave? But if I put my everyday bowl in, then the now koshered microwave has a chametz bowl in it! Is the answer that I use a glass pyrex bowl from every day since these don't need to be kashered? Thank you for your patience and for responding to this and all of my other emails.