One way to guage how much to put in the chimney is to experiment by pouring onto the grate the amount you think you'll want, i.e. enough to totally cover the grate, partially or whatever. Then put that back into the chimney and see how much you have. Thereafter, you'll know how much to pour into the chimney and light. Obviously a SJ has a small area for briqs so you don't really have much area for a "cooler space". However, some here have managed to cook indirect on one ... ? You can regulate the amount of heat by the amount of fuel you're using.
Paul