I always use Camilla to take out Oboro and that's almost it. Afterwards, I have her either ferry units or get any remaining villages. Afterwards, I have her take out any fliers getting a bit too close to the exit.
As for how i do it, It usually goes Silas to the right, Elise grabs top right village, odin/nyx snipes the bottom group turn 1, niles does the same, mozu moves right with silas, arthur and effie run to the central western wall, avatar and butler run to central east part. If you have Azura with you, you need to think really carefully about who you dance for. Dancing for niles allows you to chip at the bottom group again, dancing for butler allows you to hit the oni savages early, dancing for effie allows you to break wall early and dancing for odin can let you get the top left villagae early. This is all turn 1 btw.
I usually move niles away from the ballista afterwards because ninjas suck, and i have him take a potshot at any nearly dead enemy. Just kill whatever you can this turn, and just set up your chokepoints except for the top left. That should be left to Selena and or beruka. Once you get Camilla, have her kill anyone troubling the central area and bam. from there, just clean up as much as you can before turn 7. If you're still getting swamped by turn 7, you aren't likely to win as there will just be too much to deal with.
A lot of this will be rng, but that's basically a starting turns guide from me. Make sure everyone has vulnearies (or however it's spelled) because you'll likely need it. and remember, you don't need to hit every village. I only recommend getting the top left and right ones, but the other two are really good.