I use multibattles in mino.  Just today I cashed in a 50x and used a few energy refills from the inbox.  But fusion is done, multi were  about to expire, nothing else I really want to do.  Mino is not an afterthought for me, but it is kinda the last thing I get around to doing.  It's a great way to use energy quickly, and multi facilitate that.

I would generally always run my Multi-Battles and select "use gems to refill energy" - this is because it usually would cost you 800 gems per champion you are getting masteries for. 

Generally you want to run at least 4 champs you are training for scrolls and 1 champ that is solo'ing Minotaur. I know you can sometimes use 5 champs (if they're geared), but usually mine aren't. 

You'll need an average total of 614 runs for Minotaur to complete 4 champions from start to finish. The average amount of exp you'll get from those runs is 2,549,328. I personally start my Minotaur grind when the 4 champions are rank 5 and level 1 (5-1). And you'll almost take them to 6-60 through the grind.