With this method you can deal massive damage with least FP consumption, to make it work we need to use ash of war: Carian Retaliation and Wraith Calling Bell.
Ash Of War: Carian Retaliation
Carian Retaliation is Ash of war for your shield by Swing the shield to dispel incoming sorceries and incantations, transforming the magic into retaliatory glintblades. Sold by Pidia, Carian Servant at Caria Manor, to gain access to his chamber, you need to drop down from the cliffs in the Three Sisters location.
You can increase the glintblades damage by upgrading your shield, and it can be used on light and medium Shields, also make sure to choose magic on shield as main affinities.
Wraith Calling Bell
Next item we need to have is Wraith Calling Bell, its a ring bell to calls prowling wraiths with cost of your FP. It can be found in a chest in an underground room in the Laskyar Ruins.
To apply this method, first you need to use Wraith Calling Bell to call prowling wraiths then immadiatelly swing your shield to get 3 retaliatory glintblades. It should be noted the glintblades will automically targeted the nearby enemy. The damage is massive depending on your shield, the more you upgrade your shield the more damage it can be produce.
Always keep your distance from the enemy before using this method because sometimes you will fail if the prowling wraiths run away first to catch the nearest enemy.