Practicing Matchups

How should you drill a matchup?

For example, let's say I want to run the first 3 levels Annie vs Fizz like 40 times, vs my (apparently very good) friend. What do I do for that? If I set up a custom game, we join and play and then I guess we just both leave and the game quits? Is there a way to get out of the match before 20 minutes?

For that matter, let's say it's a 5v5 scrim but we're only running for the first 2 levels and we want to run that out like 100 times. Again how do you arrange that without running into leaverbuster issues, or hopefully without even having to shut down the client?