Build for +RES/-ATK Brave Lyn?

Hone cavalry. Not on her, but on a buffbuddy of some kind– depends on which good cavalry units you have, though Cecelia is a good f2p option if you lack other cav units. Other than that: her default bow and default swift sparrow. Keep her b slot if you want to avoid Distant Counter, replace with desperation if you want to use a low-hp playstyle (though that +res will help against mages). C slot is up to you, though if she's already going to be next to a buffbuddy she could buff them right back with a hone/fortify/goad/ward cavalry. Attack smoke is great as well if you lack the fodder.
Just my thoughts as someone with a HM-maxed neutral B. Lyn!