Re: How do you do more then one coal at once?
Looking down at the top of the bowl, imagine it divided into four quadrants. I usually put the two coals at opposite ends of the bowl (in opposing quadrants). After about 10-15 minutes I ash the coals and then put them on the bowl opposite each other again, but this time in the other two quadrants. Then I usually just leave them there and ash every once in a while.
Are you using a wind cover at all?
Have you tried using two layers of foil? I've won some heat management battles this way.
^^ Also, as dreamender said, what kind of bowl are you using?