I clean around the master cylinder fill cap, remove cap.
Then I remove the cap on the bottle of brake fluid....remove foil seal on bottle......and re-install the cap on the bottle.
Then I manipulate the bottle back next to the master cylinder fill location.
I then remove the cap from the brake fluid bottle.....and tip the bottle to fill the master cylinder.
I re-cap the brake fluid bottle, and manipulate it back out.
Finally, I put the cap back onto the master cylinder.
This works with the small bottles as well as the large bottles.
Took me longer to type this than it does to do it...which is why I prefer doing to talking about it.