I have a fleishig microwave my child put a open container dairy farina it’s spilled over, is there any way I can use the microwave again for fleishig.
In general it is adviseable to have two microwaves, and not to use it for milk and meat even if the two will be covered etc., because mistakes will eventually happen, and it is controversial if a microwave can be kashered. Regardeing your question though, according to many poskim it can still be kashered. The microwave and glass plate have to be cleaned out well, so there will not be any residue on any surfaces. Wait 24 hours from when the milchig spilled over, before kashering it. The glass plate that the farina spilled on should be kashered by pouring boiling water from an urn onto it. The microwave itself according to many poskim can be kashered by placing a bowl of water into it and then turning on the microwave until the water boils and its boiling steam will fill the inside of the microwave.
Halachos Of Pesach pg. 182 ftnt. 156 in the name of R’ Moshe Feinstein Zt”l, Lehoros Nossan 7-61(5), Hakashrus Chapter 1 ftnt. 105 in thw name of R’ Eliyashiv zt”l.