You want to open with Llyud’s EX to gain a stack of his buff. This will increase the strong auras that Llyud has. Llyud drains his HP with his hard hitting S1 and LD and regains HP with his S2 and EX so be sure to check whether or not Llyud needs to survive any upcoming attacks before draining your own health.
Free skills should used to keep AA up or S1 for more damage
Aura Spear (S1) will drain 30% of Llyud’s mHP before batterying himself and attacking. This will also battery his allies after attacking.
Crimson Wings (S2) will heal Llyud, with excess healing going to his BRV. This also grants Llyud a buff that increases his stats and allows Llyud to heal a bit back every time he attacks.
Fanfare (EX) charges slowly, taking 3 skill uses to refill. This EX will heal allies and fill their EX gauges while granting a free skill use next turn. This can be very useful to use for characters that have significant buffs, damage, or debuffs tied to their EX gauges. This also increases the stacks of his buff by 1, increasing the strong aura.
Enfuse Spirit (LD) consumes 50% of Llyud’s HP before providing a very strong battery to the party. Llyud also heals the party before attacking. This will fill Llyud’s EX gauge to max and grant his LD buff. This buff increases the party’s damage and grants Llyud Last Stand as long as his HP is above 50%.
Technical Spear (FR) is a strong, consistent boost most units as any kind of healing (regen or burst) which Llyud provides and many units have stacking buffs/effects. For those who don't, you can lean on Rydia LDCA and her Blink buff with 3 stacks to make everyone with it tick the full +60%!
If the buff/effect has roman numerals, it's a stacking effect! BT effects, Overhead effects, buffs and even Garland LDCA (no roman numerals, but is still considered stacking)