For maintaining a lower temp for low and slow, I start with fewer hot coals. If I start with too large of a fire in my BGE, then the temp likes to climb up higher than what I was wanting, but if I start with a smaller fire initially, it keeps the temps lower for a longer period of time. If you're using a chimney to start the lump, you might try reducing the number of coals in the chimney by 1/4 to 1/3.
I've been using the BGE starter cubes, and for a lower running temp, I just use 1/2 of a cube to get the lump going.
By the way, a box of the BGE cubes is $6.99. Tractor supply recently had the same thing (without the BGE name on it) for $1.99.
Tim, A Big Green Egg, 1 Butt Ugly UDS, and yes, a gasser for the quick and dirty.