Your first? I'll trim it to where you want it, salt, pepper, then 300f straight until thickest part of the flat (the middle) is 200f. Then let rest for as long as possible, if needed put it in a 170f oven.
$8/lb around here. London Broil usually refers to top round but can also mean flank. Flank is superior to top round as a steak. I'd rather have a fattier cuts for fajitas but they'll still be good.
If my memory is correct, it should have lit fairly fast, burned hot for a short time and completely. I think it's difficult to work with so I prefer high end briquettes for direct fire and kbb for smoking.