I once went through an embarrassing number of aluminum washers from a local shoppe at $1.50 a pop. Couldn't get them to seal, never could get that "squish". Turns out they were some harder alloy of aluminum, totally unsuited to sealing duty. In a fit of rage I ordered 100 proper aluminum washers from Spiegler for 25 cents each, which worked perfectly the first time, every time. I don't like using copper; they tend to turn dark or green and look weird.
Back to the original question, I just cleaned, rebuilt, and bled a system tonight using less than half a small bottle of brake fluid. But you can't count on that. Always pays to have at least two of the small bottles around, unopened.
Only squirted brake fluid in my eye once, too.
Maybe one day I'll get the hang of this.

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