In order to play multiplayer, you have to go through the tutorial "campaign" which consists of 5 parts and a final exam (a practice duel).
After you finish that, you must then play the four duels in Innistrad. Finally, you'll be able to play the multiplayer portion of the game.
There is no local play, so you'll have to find someone online. However, it is boostable.
The good parts:
1) It can be done in a player match, and you can invite your friend so you can boost.
2) When you finish a duel, you'll go right back to the lobby so you can re-up without having to find each other again.
The bad parts:
1) You CANNOT quit-to-win. If one person concedes, the AI takes over. Yep, you have to win these.
2) You have to find someone who's already gone through the intro.
3) Did I mention you had to play the games?
The most efficient way to do this would be to build direct damage decks. Red/green is probably the best option, but your mileage may vary. I threw every direct spell I could find in, plus some creatures with haste and ones that would pump up others just by being there (like haste and +1/+0 if another red creature is cast, etc.).
I timed my games at around 4 minutes start-to-start. Boosting 100 wins/person would then be roughly 14 hours (with some time built in).