So an update for flushing my 2015 SV -- the bleeder screws are definitely different between front and rear. Could have told if I had just bothered to look
Front are larger than 7mm. Since the bleeding sequence starts with the front wheels*, I didn't bother with any of the speed bleeders and just relied on the "submerged hose" method. I should have gotten a screw gauge so I could update the thread with the size of the front screws; sorry about that.
* -- so this is something to note; sequence is different depending on model year
. Between 2014 and 2015 the bleeding sequence changed to Right Front, Left Front, Right Rear, Left Rear. In 2014 it was RR,LF,LR,RF Goes against traditional advice, but engineers must have had a reason for all this so I went with it.
Also, the service manual doesn't explicitly give a "flush" procedure. There's a "drain", a "refill" and a "bleed" procedure.
"Drain" doesn't specify a wheel sequence. It also starts with disconnect of the ABS, or IBU or 12V battery. Distinctly different from the specified "bleed" procedure, which says start the car in accessory mode (presumably with everything else connected). I didn't really want to go over the car twice, so I followed the "drain" procedure moving from wheel to wheel in the bleed sequence, and since it allowed me to develop pressure with the pedal I let it serve as the bleeding step. Had I ended with a soft pedal I would have gone through the bespoke bleed procedure using the time-tested "helper" method.
More specifically - drain procedure states close all doors and hatch; make sure "room lamp" is off, wait at least 3 minutes and then disconnect either the ABS actuator harness, the IBU, or the 12V battery. I went with the 12V battery. I assume this somehow allows proper fluid flush of the ABS, but the manual doesn't give up its reasons so easily.
I used this bleeder bottle, which is convenient. You could of course make your own with tubing and a gatorade bottle https://www.amazon.com/gp/product/B000W7F2GI/
. I hung the bottle so that the tubing rose away from the bleeder screw before descending into the bottle. This gets any bubbles away from the screw opening so they're not pulled back into the caliper.
After slowly pumping each wheel enough times to get clean fluid out of the calipers, I turned the bleeder screws so that fluid could barely flow, and then did a few more pumps with the increased pressure to force out any remaining air. The brake boost was of course off with the car asleep, so you need some leg strength for this.
The fluid was about 2 1/2 years old. The difference in appearance was enough to know when the line was fully flushed. The old fluid looked like iced tea; the new fluid looks more like pale apple juice.
After a test drive the brakes felt fine; took the car to a road where I could do a number of high-performance stops and also exorcise the ABS.
Ended up using just over a quart of fluid for the complete flush. There was plenty left if I had needed to re-bleed. FWIW, here's the fluid I chose https://www.amazon.com/gp/product/B07338GQM8/
Of course you can just go to the parts store and get the big bottle of Prestone DOT3 for cheap and still be fine.