OldIHC

I selected a 2007-2011 Toyota Master cylinder for my R series Disc brake conversion. I wanted to use my Motive power bleeder but didn't have a cap for a slip on Toyota reservoir. A quick rummage through my scrap steel shelf and I found the perfect pieces with which to build my adapter. The inner collar is a strut spacer from a VW. The outer sleeve was an exhaust pipe adapter. The top was a scrap of 1/8" steel plate and the nipple was a brass NPT to JIC adapter with the JIC end turned down to a nipple. The O-ring just fits in the sleeve and rests on the collar. The bar was some scrap 3/16" plate. The tension strap was made with 2 1/4"-20 flat head screws and a couple of washers welded into the slots.

Works great!

I worked at a shop for years that evidently had the only brake pressure-bleeder in town. All the other shops took turns borrowing it. It was gone, A LOT. We were puzzled.
We did plenty of m/c work. Why didn't WE use it?
Well, because we valued our time more than that...
Gravity does a pretty good of bleeding brakes. When installing a new M/C, if you bench-bleed the air out properly you can just burp the lines at the m/c. You're done!
For those really hard-to-bleed vehicles, using a new plews oiler filled with brake fluid and pressurizing the brake line back to the master cylinder works great.
BTW, these new ABS-equipped vehicles often take a bi-directional scanner to open up the ABS solenoids in order to bleed.
If I've ever used a pressure-bleeder in my life I've forgotten. Maybe in the 1970s
Everyone has a different way of doing things. I get that.

I read that some( maybe all?) OEMs fill brake systems on the assembly line from the calipers. I can see where it makes sense. You're forcing fluid and air bubbles up to the highest point
Instead of trying to drive the air down to the lowest point.

I can recall only using pressure bleeding once in my long time as a mechanic. Most often if a wheel cyl was be changed, I just worked quickly and kept the master full.
The one time I used pressure it was on a Saab 900 clutch, and it turned out it was not air that was the problem but an incorrectly assembled pressure plate, 2 of the "fingers" on the diaphram spring were behind the pressure plate so could apply pressure but not retract the plate when the pedal was pressed. Took a lot of hair pulling to find that one.
Even on my K's with the Hydrovac, gravity does a fine job and allows you to go onto other tasks, only remembering topping up the master is the only draw back to the method.

The "advantages" to a power/pressure bleeder are these: only 1 person required, constant pressure on fluid, so bubbles in system are pushed out each line bled. Used it often when in the Military.
Not sure if there are other advantages. Those are the two main ones I can think of. I acquired a pressure bleeder about a year ago, and sold it two weeks later to a mechanic.

Just this old fellows thoughts.

Ha! Lloyd, I just see "desperation". like, you've tried everything else...

A short story:
My genius junior college automotive instructor told us a story when he was service manager at Cadiilac.
They had replaced WHEEL cylinders on a car...
Keep in mind this guy is scary smart...
They COULD NOT get good brake pedal. EVER. Readjusted brakes a dozen times. Bled brakes fifty times, etc. PRESSURE BLED AS A LAST RESORT.
No help.
Customer on the phone "WTF is my car???"
Mr. Parlier instructs his mechanics to...get this...."rebuild the new wheel cylinders deep in a pot of fresh brake fluid".
And they did! HA! What a mess!
NO HELP.
FINALLY, genius Mr. Parlier gets his pocket caliper out and measures wheel cylinder diameter.
Wheel cylinders were wrong, INTERNALLY. Looked perfect, externally.
THIS is where I learned to always double-check advertised cylinder bore on any m/c or w/c.

Twenty or so years ago a local BMW service and repair shop was selling of a bunch of equipment. I bought the pressurized thingee for brake bleeding. I need that, I thought. In a fortnight I had it sold to one of the guys from work. I am a gravity guy. I always open the bleeder screw on a caliper and blow out into a bottle then add fresh to the MC.
I always use DOT 5 on any new or rebuilt system. NEVER SHAKE UP A CONTAINER OF BRAKE FLUID. The bubbles take a long time to rise out and DOT 5 may take several days to clear. Spongy brakes are most likely from the bubbles compressing.
I never turn drums or discs. I buy new premium from NAPA.
Here is another good brake bleeding tip. On an old system where the master cylinder is going to be used, it is very likely there will be rust in the master cylinder just beyond the usual travel of the MC piston. If the pedal is depressed forcing the piston into the rusted area,a the piston seal will be destroyed.
My home made tool for this job is a wood 2X4 about 6 inches long. I fasten the 2X4 to the pedal with a spring clamp to restrict pedal travel. Remember when pumping the brake pedal, slow and steady.