This video was pretty helpful for her trials. As mentioned in the description for the upload, the idea behind trial 4 is to use HCB, f+C --> HCB+A/C as a shortcut for the Crow Bites --> Freeze Execution cancel.
Some notes regarding Counter Shell:
-all versions cause counter wire (not just EX)
-causes ground slide, which can't be recovered from with safe fall (recovery possible with hit by counter wire or reflected projectile)
-reflects special, EX special, DM, and SDM projectiles alike; works on multi-hit projectile DMs like Ash's Thermidor and Saiki's Tokoyami no Fune, but not Elisabeth's SDM Noble Blanche
-shard from EX version hits 3 times, as opposed to the usual 1
KoF XIII // Kula/Iori/Mature | 3S // Dudley (SA I) | TvC // Saki/Tekkaman Blade | BB // Tsubaki, Noel, Valkenhayn | MvC3 // Dante/X-23/Amaterasu