Hello,
I have quite a bit experience with CO poisoning, attempted twice and failed obviously. I don´t know the size of your room or the amout of charcoal you are going to use but I lit one disposable grill in my small bathroom. I guess you have to wait until there is no smoke left. Personally I didn´t wait and coughed a lot. Felt dizzy and fell asleep. It´s important to seal anything that can lead to gas leakage e.g. with duck tape. I can´t tell you any more but I hope it helped. I would also suggest renting a cabin or doing it in a sealed tent because otherwise your neighbours might be affected by the CO. The effects of the poisoning itself weren´t painful in my case. I woke up 4 hours later with tachycardia and a slight discomfort. I also panicked bc I didn´t expect to survice. So I would recommend the method but will take a lot more charcoal next time.