Creating Explosion effects?

Anyone know of a tutorial for making custom explosion effects or whatever? I can't seem to find anything on effects creation at all. I'm trying to make a fiery explosion that lights players and vehicles, etc. on fire when it hits an area, but I've no idea how to A. Boost the effects so it's not just the lingering flame from the flamethrower nicking their heels and annoying them, and B. How to increase the size of the explosion without the smoke becoming a gigantic useless rolling bitmap floating over the ground.

The explosion is for something alike to the Halo 3 Firebomb grenade, only larger and not as instantly lethal.

http://hce.halomaps.org/index.cfm?fid=3034

That's the closest thing I've seen to a custom particles tutorial. I've been looking for help on this too.

Thanks, hopefully I can figure out what to do from here.