I've created this guide to put down any know time-saving bugs. Tell me if you find anything else.

Disjointed gun If Shiso uses a step spell and then uses his gun right after, the first shot will not trigger the proper animation, allowing him to act while firing. This include shooting, and strangely, if the attack button his held, you can fire twice as fast for as long as you want, and this effect stacks. You can also move while keeping this, but if you are not careful you will lose this effect.

That's all that I know of.