I seem to have *stumbled upon a amazing "mechanic" (its a bug, but im calling it a mechanic) which allows something to happen which I have dubbed a flash charge. What a flash charge is is just a second instantaneous charge following a charge you have just finished (IE: 2 charges in roughly the same of a normal single charge).
How a FC happens is a little odd and focuses on what statuses you currently have (buff or debuffs, both work here). If you finish a charge just as a status is done a second charge will occur, the flash charge. Note however that some weapons do not have flash charges and not all statuses work (IE: poison does not while stun does). Getting a FC off with debuffs is difficult and not always reliable, where as buffs work great as you can practice to have the timing down perfectly (or as you will see, it times it for you).
To do a flash charge requires a few things:
Deadly Shadow Cloak or Frenzied Firestorm
High-Max CTR (Max works better, as the faster you can shoot the more likely the FC will show up)
FC compatible weapon (I will need help to test what weapons work and which ones dont, list below)
1. Activate cloak, at the same time charge up your weapon (breaks cloak and instantly starts charging) demo screenshot
2. As soon as you are charged release (if you do it too late the buffs will leave without a FC) demo screenshot
3. If both 1 and 2 worked you will have a Flash Charge which looks like this. Aftermath
As you can see it is simple enough to do but will required a bit of practice to get the hang of it. There is another way to break the cloak as well as charging instantly. Cloak-shield-hold attack-press shield, this will break you out of cloak any time you wish. Note though that doing a Flash Charge will keep you stationary a bit longer than normal so be wary.
Working flash charge list:
Blitz (tested max CTR, FC is hitscan)
Hammer (tested max CTR, Only the first blast occurs)
DVS (tested max CTR)
Acheron (tested very high CTR, only sword swing occurs, no blasts)
Gran Faust (able to fire off the blade and is immune to self curse damage)
Not working:
Polaris (tested max CTR)
Master blaster (tested VH CTR, need Valiance to be tested)
*stumbled: I saw a video on youtube (pretty sure it was zeddy) of two blasts going of a single bomb after stun debuff deactivated. I research further but nothing showed up so I did some solo testing, thus the flash charge was found.
Side not: Bombs work with flash charges but are very unreliable as you need to time the blast with the deactivation by yourself.
I dunno if flash charging bombs works with buffs, but the window is fairly lenient with stun. As far as I can tell, you just have stun wear off while the bomb is out.
I never made a video about it, but you're probably thinking of the gif.
I think Valkyrian Aura with its CTR buff has the ability to FC as well.
Edit: It doesn't. Your buff/debuff needs to affect ASI.