Do you guys have any advice for grinding up Maribelle/Lissa, both in support and levels? (I'm going w/ Donnel x Lissa and I haven't decided for Maribelle)
For supports just pair them up with the person you want the to support with and play like normal.
For levels, the best way is to buy Rescue Staves. Go into a map like a Spotpass map or a Risen encounter. Kill every enemy except for 1. Have 4 players surround the last enemy and unequip their weapons (but make sure they're tabky enough.) Have Lissa/Maribelle away and have them spam the Rescue Staff on another character. Even better, just have them spam it on each other lol. But if one of the guarding characters takes too much damage, you can heal them normally. Most enemies will only focus on 1 character so you shouldn't have to worry about switching spots or anything.