Overall Concept
You need to give
Shinku constant field time, since she loses her Ultimate once swapped out, so we must build around this restriction. At the same time, you want the Charge reaction to keep going.
With
Shinku's very long rotation of 15-second+, she builds her own Esper Meter, so she can trigger one reaction - either Remora and Blossom. Other reaction should be instant with
Zero, to not waste much time on allies rotation.
Instant Esper Meter Refill
Zero’s skill grants 100 Cycle Energy upon use, which fills
Zero’s Esper Meter in one go. You're better off saving this to use after other allies rotation, and after triggering Remora with
Shinku. Since Remora lasts 12 seconds with
Hathor, and Blossom lasts 10 seconds duration.
The goal is to maximize Charge uptime while
Shinku is back on-field.
Natural Esper Meter Refill
By the time
Shinku completes her long rotation, her Esper Meter shall be full. Don't swap directly from
Shinku to Anima or Lakshana. Instead swap to
Zero (a Cosmos character) to delay the reactions until allies' rotations are finished and you're ready to bring
Shinku back on-field.
Both Anima and Lakshana characters will rarely fill their Esper Meter, so we don't count on them in the rotation. But if they happen to fill it, you get a bonus reaction (preferably extra Blossom for more DPS)
Ultimate Energy Gain
Shinku doesn't gain regular Ultimate energy, instead she builds up "Defiant Spirit" energy through her normal attacks, charged attacks, dodge counters, and triggering Menacing Gaze.
The easiest way to fill her Ultimate energy is by not attacking, dodging enemy attacks, and delaying counters until Menacing Gaze stacks are full. Then unleash a dodge counter or a skill with a full stack of Menacing Gaze. From there, spam dodge counters and skills until Ultimate is ready.
Against aggressive enemies, this can be done very quickly and
Shinku reach her Rampage/Ultimate in no time.
Allies' Ultimates will also be ready quickly, thanks to
Shinku enabling Charge to be shared with the entire team.
Maximizing DPS of Shinku Passive
Her passive "Lone Strider" requires
Shinku to be the the active character during the Charge state. So we need to trigger Remora, then Blossom, then quickly swap to
Shinku.
Each Charge trigger increases her ATK by 5% (up to 10 stacks), and she follows up with an AoE attack that scales with
Shinku basic attack level.
By default, Blossom buds lasts for 10 seconds, and shoots every 2 seconds, for a total of 5 stacks and AoE triggers. With
Nanally's passive, the trigger frequency is doubled, for a total of 10 stacks and triggers.
Maximizing Menacing Gaze burst
Menacing Gaze is a character trait exclusive to
Shinku, enabling her to build stacks passively by being in combat and not attacking. By default, she needs 2 seconds of not attacking to start building stacks, then 8 seconds to get full 8 stacks. This takes a total of 10 seconds.
Against aggressive enemies,
Shinku can spam dodges without counters, building an extra stack with every dodge for a faster buildup.
The next attack she performs will trigger Menacing Gaze for a massive burst that scales with the number of stacks and Normal Attack level. It also grants Cycle Intensity, and either Defiant Spirit or Fading Reason depending on whether Shinku is in Rampage or normal mode.
Not attacking might sound counter-productive, until you realize she ca build it start of the fight before approaching the boss or initiating the timer. Can also be built while the boss initiate their stalling mechanic (by flying away, diving underground, being invulnerable, or unleashing several hit combos).