The fast and dirty.
OK here is a screen shot, I used the fifth post. I never aim at their feet, I get the circle on the closest soldier. Then I move down and to the right between soldiers until the green circle is gone. I wind up about 3/4 the way, and let it go - stink bomb, so it hits all. Then I immediately switch to explosive, and green circle the officer. After practice you can hit him, any case you aggro him when throwing.
Hitting any of the other soldiers on the path usually breaks the group and they come through the fence. Use fire near the end of their health, so you get use of the grenades, but doesn't have time to do a lot of burning damage.
screenshot_2009-2-10_13-13-36gren.JPG
Hearing about outcast working again that is a place many like to go next, hiding in the rock hitting stumps.
Really, at this point grenades should be used with all other missile combos and worked together on Darkhart or something. Multiple weapon rep, max for each one.
If racing through the character like I did on this one through all the quests, this is like day 4. One more level to padres quest.
All you wanted to know for grenades. UGH, guess I could throw in the big alligator in Tortuga swamp, is glitched to get grenades to long volley.