How to use DLC Boss weapon ashes of war on mnk. [spoilers]

[Yazz]

Hello, I'm trying to use Renalla's ashes of war on mouse and keyboard but it seems hard to do blue waves attack. It's supposed to be strong attack when charging for aoe - which works, but when I try to do what's supposed to be mentioned waves - when charging use light attacks it just stops/starts normal attacks. the issue I have is that for ashes of war to charge I have to use shift + rmb, strong attack is shift + lmb and light attack is lmb. which doesn't work too well together, cause when I want to do light attack when charging - I have to stop charging. help please.

[Yazz]

I had to rebind default keybinds.