Farming proficiency EXP: Prolong low-damage fights and retreat before the killMinor spoilers
Choose a matchup where you can deal damage without taking much in return. Use low-Might weapons to extend combat, retreat before defeating the enemy, and repeat.
Original video: Fire Emblem: Fortune's Weave — How to farm proficiency EXP quickly | Bilibili creator Xianyun SS
Proficiency EXP requires combat that deals damage
First check whether the attack actually deals damage. Two hits from a follow-up attack in the same combat still count only once. Efficient farming means more qualifying combats. Do not weaken your weapon so much that it stops dealing damage entirely.
Each use’s gain has four components. Base experience for the corresponding weapon is 1, a strong subject adds 1, neutral adds nothing, and a weakness subtracts 1. Fully unlocked Boons of Salvation add up to another 3.
Base points + proficiency strength bonus + class bonus + Boons of Salvation bonus = proficiency EXP earned.
For example, 
Ludia is strong in swords, neutral in gauntlets, and weak in axes, so each weapon gives different returns. Add the class's favored proficiencies and Boons of Salvation to determine the final award.
WarriorThese returns include the example class and Boons of Salvation bonuses. Higher development ranks require more EXP, so training several units to Divine class requirements takes dedicated time.
Low damage in both directions suits EXP farming
Make contact in a dungeon to start a Clash, then compare several units. Look for someone who deals little damage and also takes little. 
Dietrich can suddenly land a critical hit and kill the enemy, making him less suitable for prolonged fighting. I settled on 
Esmeralda, though her damage was still high. Single-digit damage would be more comfortable.
After checking candidates, retreat, return to the title, reenter, and test another ally. Once prepared, start repeated engagements:
- 1Contact an enemy in the labyrinth to trigger a Clash.
- 2Fight with the selected low-damage, low-damage-taken unit, confirming attacks still deal damage.
- 3Retreat when the enemy is nearly defeated.
Use armored classes and wooden weapons to reduce damage
Try 
Armored Knight for training. Low Speed reduces the risk of a follow-up attack killing the target, while high Defense eases repeated incoming attacks. Equip low-Might weapons such as wooden ones to minimize damage per combat.
Check both sides of the actual forecast: the enemy should survive many hits, your unit should also survive, and attacks must still deal damage. That combination keeps the exchange going.