I was also confused when I first read the instructions.
In the end, I was able to do it myself by tipping the
container and it was not too difficult.

I suppose you could unscrew the lid releasing pressure.
But, brake fluid is corrosive and you really don't want it on
painted parts or electrical parts and I think you would
spill some trying to remove it while the resevoir.

Also, it does not draw fluid back when you release pressure.