I've spent an inconvenient amount of time and money trying to bleed my brakes myself. I did it one time over the summer with the "standard" procedure (at this time I didn't know that these cars had a weird brake bleeding sequence) and got a perfect pedal, seemingly completely by accident. A few months ago though, one of my wheels went into a ditch, and I guess it dislodged a bubble because my brake lines because they've been persistently spongey since. I bought a harbor freight vacuum bleeder (did nothing), and then i tried buying external check valves to prevent air from getting sucked back into the bleeder screw (two cycles of the nissan sequence and the "traditional" sequence changed nothing). I now have few options left:
Buy a pressure bleeder
Do a proper two-man bleeding procedure, and then cycle the ABS by getting up to speed then slamming the brakes.
Buy an ABS capable scan tool, and cycle the ABS solenoids.
Or completely fold and bring it to a brake technician.
ChatGPT is firm set on the idea that there's air in the ABS module (I really hate AI, it's so confidently wrong in so many things), and then redneck bleeding the ABS (slamming on the brakes a few times then bleeding again) could fix my issue. I'm not 101% sure it is the ABS module but it's seeming like the biggest possibility right now. I have seen someone mention years ago on these forums that you don't actually need a scan tool when bleeding the brakes, but I haven't seen anyone else agree. What would be my best option here? Get a motive power bleeder? Have a buddy help me? Buy the scan tool and return it? Or fold and bring it to a technician.

 

update: bought a foxwell NT630 plus because im cheap.
cycled every ABS solenoid multiple times, cycles the motor multiple times, and went 3 ways around the entire system. not a single air bubble came out, but the pedal STILL sinks. im so ****ing lost right now, idk if im doing something in the wrong order or whatever, but it's really getting on my nerves, because i daily this car and im not comfortable with having spongebob as my brakes, especially with passengers.

 

I have pretty much the same issue. I had a slightly squishy pedal last year so figured it was time to replace the brake hoses with Z1's stainless ones. I have the FSM so was aware of the bleeding sequence. Even using my Motiv power bleeder, the "proper" sequence, and cycling the solenoids with NDS2, I still couldn't get a firm feel after multiple rounds of bleeding. I hate to blindly throw parts at a problem but ended up replacing the master cylinder out of frustration. After multiple rounds of bleeding it got slightly better but still not good. By then it was time to put the car away for the winter, so I'll be re-visiting this again in a couple of weeks. Sorry to not be of any help, but you're not alone.