Ralph is dead on about the fire. You want to ignite a small number of coals and then let the fire progress as needed throughout the cook. I have a large BGE too and use the following to get rock stable low and slow cooks for up to 18 to 24 hours:
1. Fill bottom with coals to just below the line separating the fuel bowl and the spacer ring
2. place electric coal starter on top of coals and grab a few coals from the sides to just cover the surface of the starter
3. let the starter run for a few minutes until the top coals are ignited
4. remove starter and insert indirect heat diffuser
5. close lid, open the top vent so that the daisy wheel has all of the holes open
6. Start HM
With BGEs, it is critical that you make sure that all of your grate/coal box holes are patent and free of coal dust. For the HM, I personally use fan/servo combo because I have had nothing but excellent results with it and it gives me the peace of mind that if something goes wacky with the fire in the middle of the night, I have the fan control to overcome it.
1. Fill bottom with coals to just below the line separating the fuel bowl and the spacer ring
2. place electric coal starter on top of coals and grab a few coals from the sides to just cover the surface of the starter
3. let the starter run for a few minutes until the top coals are ignited
4. remove starter and insert indirect heat diffuser
5. close lid, open the top vent so that the daisy wheel has all of the holes open
6. Start HM
With BGEs, it is critical that you make sure that all of your grate/coal box holes are patent and free of coal dust. For the HM, I personally use fan/servo combo because I have had nothing but excellent results with it and it gives me the peace of mind that if something goes wacky with the fire in the middle of the night, I have the fan control to overcome it.