I know some things are specific, like Honda, you use only Honda ATF fluid, maybe even their powersteering units, have to use Honda fluid. I want to flush out my 2010's brake fluid but Toyota fluid is expensive and will take too long to get here. While autozone has some dot 3 for $8~ that's 32oz while Toyota DOT3 is $10 for 12oz. Does it matter what brand I use for brake fluid in my 2010 Prius?
No, as long as it meets the DOT 3 specification (Owner’s Manual (PDF), page 564: “SAE J1703 or FMVSS No. 116 DOT 3”). Keep in mind that you’ll need a Toyota Techstream diagnostic system (or true equivalent) to bleed the brake system.
There is a non-Techstream method outlined in the Repair Manual. @NutzAboutBolts follows it in his video, apart from jumbling the order a bit. The diff is basically that you put the car in "invalid" mode before starting the bleeding. Up here I get the the Toyota DOT3 in pint (16 oz) bottles for around $7.50 CDN. A couple seems to suffice; I can't find system capacity anywhere. Edit: I think they're pints. It's something like 470 cc, I can check.