you can get more exp tickets from the higher level map supply units. each higher level map supply unit gives 1 more small exp ticket, to the point that i'm currently getting 7 from one run at the lvl 35+ map's supply unit. and when I do the lower tiers as well, i can get like 40 a day.
sorry, you're right, it's specifically nuns. I just threw them together when I translated since most of the others usually include the entire section of the class tree (primarily split between japanese/western of each unit class)
also, the problem with the dojo is that units you throw inside cannot be used in your attack/defense teams, hence I use it to level the high-tier units I'm going to use while using the already leveled units which are currently making up my core team.