To add to this, and you can do this if replacing the pads, get some method lined up to first suck some fluid out of the master, so that there is room for the fluid. I actually bought a couple of big old medical syringes off ebay BUT THEY ARE GLASS. You can use them with about anything and it won't hurt them, unless you drop them.
i use a plastic dirt bike fork oil syringe, they do a great job of containing the fluid and super cheap. what's great is that you can just toss 'em in the slop sink to rinse and not sweat it, and if they get all nasty you can just throw them out.
