Got my Shiki up to 90 and maxed her skills. In this method, I used two Tamamos instead of 2 Wavers. Since both Tamamos had maxed Foxes Wedding, thats double Arts damage.
If you put Formal Craft onto Shiki as I did, this method would give more damage versus the other method. Also since Shiki ignores defense anyways, theres no need to lower enemy defense twice with Waver.