how did it go?
Fellow had 1 hour to spare, explained the rules, then played some 3 turns until Montevideo fell. He saw the whole shebang - Transport and how vital the rivers are, Movement and necessity of having the Commanders with the armies, Conquest of spaces and winning cards and victory points ( depleting any of the decks signals end of game ) and applying the cards effects.
Some extra explanations on the background were given and how it relates to some of the rules as the nations have their own particularities, especially Paraguay.
All in all not what I expected BUT was a good practice to GM and teach the game in the future.