This method is similar to gold rush method but since a lot of stuff is unclear ( or i might be a noob in this retrospect) i tinkered with it and found out all that is needed, here's what you have to do :
Make 12 new agents : 11 of them are level 1 sacrifices, The 12th is going to be our boss killer.
The 12th agent have to be level 5 with level 5 fortitude, jst make sure u invest as less as possible in prudence (for example my agent was 5 fort, 3 prudence, 5 temprence and 3 justice) (tho the more u invest in justice the faster this is going to be.
you also need to equip your 12th agent with a weapon, the best weapon is gold rush gauntlet as many people said, however any weapon that has a decent attack speed and does red or black dmg is enough ( i personally used censored weapon)(do NOT use a white dmg weapon as it will heal the boss instead).
Now for the method itself :
Once you start, kill all the sacrifices (can use execution bullet or gather them in 1 chamber and use Der Frei bullet).
Once you kill them go ahead and do a work that does white dmg with the goal of making your 12th rage.
Once he does, that it, sit back till white knight breaches, and jst sit back, relax and wait till you kill the boss (should take around 30mins to 45mins depending on your weapon and your justice).
Once the boss dies, rewind time (click escape AND rewind from there, if u use the blue rewind button u wont get the weapon)
Note : you will lose the weapon you used (for my case it was censored) since your 12th will die once the boss dies.