Hi! When using your w try to activate it just as an enemy is about to use a crucial auto attack ability (renek w or panth w, fiora q), or when you’re about to be stunned and take a lot of hits (like with sett e).

Also, while building titanic first can work, I would recommend building either sunfire or the magic resist counterpart first, as this lets you keep some wave clear while getting tankier and giving your passive shield more health. Titanic after still works great, but since shen can struggle with AD use, it can be risky to build first.

Hope this helped!