https://sanctioned-suicide.net/threads/failed-co-method-2-times.37021/
To get a higher CO level one might need more coals. If you read the megathrad as you say you would know the length of time suggested to burn the coals and what they should look like before bringing them into the bathroom. There are multiple pictures from previous failed attempts showing what they used, where and how, paying much attn to the details but could still not be successful.
If this was an easy method i would have used it already. It's frustrating. If i was attempting this method, i would use a lot of coals, and only the ones suggested.
EDIT. I copped this from the megathread.
First of all, you need to buy "premium" charcoal. The two most common type are lumpwood and briquettes. I would highly suggest to use quality briquettes over lumpwood. The consistency of briquettes make them a lot easier to light and they smoulder longer than lumpwood and burn cooler. They do have a bit less carbon content, but in the end it's not a big deal. Also, contrary to popular belief here, quality briquettes usually produce less smoke too.
Only use a chimney starter to light the charcoal. You may be tempted to use lighter fluid — but don't. This is the only way to ensure perfect glowing briquettes that will burn at the same rate. Just use some crumpled sheets of newspaper on the bottom of the chimney and light them with a match. It takes about 25 minutes to get them at the proper state. Once they are ready, you can dump them in a small portable charcoal grill [Edit: or metal/galvanized steel bucket or tray]
. You want the charcoal to be fully white (45 minutes for Royal Oak Ridge) before you bring them inside. Don't put the cover on obviously. If using benzo/alcohol just go in, drink your cocktail and pass out. If not, let the charcoal sit for 20 minutes inside the room before going in.
1KG = 2.2lbs is plenty for a small space like a car or tent. If your room is bigger, double the amount. For 1KG you'd need approximatively 35 briquettes.
The location is obviously extremely important. The smaller the area, the better it is. Carbon monoxide will fill a small space at a high PPM much more quickly. It can also travel through walls so please make sure no one else is present. Apartment and hotels are a bad choice for this reason. They can also have CO alarms installed. Always make sure to seal the area well. Put a blanket under the door and use ducktape around door/window seams, fan vents, holes, etc.
