my advice is to get the tool from autozone, or pepboys, or whereever they sell auto parts, it's very common, works easy, doesn't damage anything and doesn't take up a lot of space
I can't remember the name, but I'm certain if you tell them what you need, they will have it, if you ever plan on doing brakes again, you will definitely need it
and yes, you're supposed to release pressure in the system by opening the master cylinder, you may want some towels handy in case brake fluid spills over and close the master cylinder reasonably quickly as the fluid absorbs water in the air