Here's a pic of leftover coals from a cook. All of the leftover will be easily used. I simply lift the basket and shake out all of the ash.
After shaking the most burnt coals along with partial burnt chunks will be my starting fuel of the next cook. I line it up most burnt to least burnt, then fill in with new. It never takes much!
This gives me a hot clean start with TBS from the get go every cook and every bit of old is used up. I light the pre burnt coals and it burns evenly from one side to the other.
Here is another example but this is in my Jimmy (Jumbo Mini) I really piled my small bits of leftover up tightly into one spot, I did a hot 300* plus cook for maybe an hour and then seared. The cook didn't even eat into the new charcoal.