There is 2 Tutorials Available for Joker Doom :Tutorial by EssentiaFour – Tutorial by CreativeEly

On glitched categories, Joker Doom is what primary kills bosses and go through the game, so understanding how it works and knowing the backups is important. For this instance, we are using the Cranes Boss Fight as a example on how to do regular Joker Doom. The concept is the same for every fight (Except for a couple of bosses, but are not really encountered on the speedrun, like Inferno for instance). It is important, at least for this fight, to wait until both sites attack to adjust what to do. Sometimes they can kill Setzer which in this case, you will have to rely on a backup below. If you would like a visual on how Slots are laid out, Click Here.

This is a straight up regular Joker Doom. You simply use an Echo Screen to manipulate it, and just use Joker Doom right after. There is a wide window on getting the 2nd and 3rd “7” since the game helps you get them. Simply practice them, and you will be fine. If you are not comfortable getting the 2nd and 3rd slot, you can do the Baby Strats posted.
Note : You need to wait until Echo Screen’s animation is finished before confirming the first “7”, otherwise it will not work.

If you fail slots the first time, there is a backup to have another chance at getting it by using Potion + Echo Screen + Failed Slots (In whatever order you want). For failing slots quick, just Hold A.
Note : It is preferred waiting to use Potion for last to use on Setzer in case he is taking damage, for the Crane fight at least.

If Setzer dies (For instance getting crit in the back from a physical attack in Cranes for instance), it is possible to still get it, but you can easily die. Just pray. Setup is using a FenixDown + Autocrossbow. Both of those are making the Slots possible, and since it is not possible to revive Setzer without using an item, we have to adjust and use something different. Using Items mostly affects slots RNG.

This is the Baby strat. It is the same as the Regular one, but you simply pause buffer each one of the slot, making it a lot easier for newer runners. Below an example.

If you are a man and don’t care about anything, do this without buffers. Good Luck.

Reverse Joker Doom

Reverse Joker Doom tricks the game into using 7-7-Bar (Which is supposed to cast Joker Doom on your whole party) into any boss in the game that are immuned to 7-7-7. The concept for it is to have Setzer have 7-7-Bar queued up, then being Muddled and getting him out of it before he casts it. That way Joker Doom will hit the enemies instead of your party. There is 2 setups possible to achieve this, one using Remedy and the other using a physical attack. Casting Vanish makes the Muddle spell hit 100% of the time, and you do not want Muddle miss because if you 7-7-Bar and Muddle miss, it is Game Over.
Note : The Item “Remedy” does not cure Confusion, only the spell is able to.

Glitchless Slots

For Glichless categories, you can use 7-Flush and Chocobop in order to do damage. Those are not affected by Slots RNG. You will only require to get the first one and just Hold A to get the rest of it.

Understanding Slots

If you would like to understand how Slots works in the game and what affects 7-7-7, Here a very detailed guide made by MasterZed.

There is also a document made by cleartonic to help you understand the Timing of Slots. Please note that it doesn’t take into account pause buffering.