I presume you've read this post?
http://forum.shrapnelgames.com/showp...29&postcount=6
Now, to re-use those battle-scarred troops, simply load the "Saved-game-turned-Scenario" on the Scenario Editor (aka Game Editor), and from there redraw the maps, and delete, add & deploy units for either you or the enemy's (using the BUY and DEPLOY buttons there). And you're done for the next battle.
Keep in mind the Experience/Morale rating doesn't increase if using this method. For that you need the Campaign string mechanism.
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Now, if you're talking about re-using troops that are still fresh, it's simpler than that: load a Scenario on the Game Editor (Scenario that contains the troops you want to re-use). And then re-draw the maps, add/delete units, and deploy the troops, all using the buttons on the Game Editor. And then save it under a different scenario name. All without playing and saving and converting the saved file into SpScn file, as in the previous method.