Smoke Generators

Was reading Defense of Hill Somethreedigitnumber, sorta a modern-day 
Defense of Duffer's Drift by someofficer (It's 1 AM and the book is 
upstairs.  This is as coherent as I get).  It's about a Ranger who eats 
3 MREs in one day, which kills him and he goes to Purgatory.  Well, 
suprise, Purgatory is at Fort Irwin, California.  Anyway, in last 
scenario, the one he gets right, he uses a Chemical Platoon's 
M-113-mounted smoke generators to screen an attack.  And TC's Armored 
Cavalry also mentions M-113-mounted smoke generators as part of an NBC 
company.  Now, as an Engineer, I worship the Gods of Smoke.  But as a 
light type, I've never seen these things in action.  But they sound 
good, and I want 'em on my Dirtside II table.  I figure it can lay 
smoke out the back, no problem.  12 or 15 inches of smoke in relatively 
thick cloud (rather than measuring radii, when someone shoots smoke 
fire mission we take cotton balls and pile them along the line of fire 
until it looks right.  But we're informal) each turn.  My question is 
how to point these puppies?  Any suggestions?  And how many turns of 
smoke can each one lay before it runs out?

John M. Atkinson