Re: Just bought a AF Solid - having some problems.
Two coals is the minimum unless you have a really small bowl and use the correct hole pattern. My smallest bowl is not much larger than the largest side of a CH coal so it can work with a wind cover. But two is ideal. Allows for great heat management possibilities depending on where you place them and on what side they are resting.
Regarding the purge valve, I suggest taking a C wrench to it as suggested earlier and checking if the ball bearing is actually in there. Is is a light hiss of air getting through or is it just open? The ball bearing may be stuck in the purge cap as often happens with my KM. Tap it, opening down, on the table and it should come out. If it is entirely missing it's good to replace a ball bearing with a non-biodegradable airsoft BB. The "green" BBs are made to break down with moisture and eventually melt away when used in the woods so that is not a good option.