Now that you have been informed the YOU NEED A FUZZ! You will notice that there are many fuzzes....
Many....
For Doom standard kit is a type of Big Muff Pi. There are 100s of threads on Muff variants. And many opinions, all I will say on this here is stay away from the Bass Big Muff [I don't like how it sounds] and a NYC as it's lows arn't as boomy as one would want for everything.
Now My suggestion:FuzzHugger(fx) Great Wall, it is SO doomy and chewy and BIG and FUZZY!
This is how most people go for drone but what happens with this approach is you end up with wet fart which doesn't really have much low end and gets completely dominated by guitar.
The way sunn do bass live is get as much power and cabs as possible so they can really push big clean low end then use a rat ( rats don't clip low frequencys anywhere near as much as a muff does) or pedal with similar gain structure so the low end stays clean and brutal. Clean blends are always a big help aswell.