Remove glass fuses without breaking them?

No need or benefit to pull both cables, just pulling one cable does exactly the same thing: cuts power to the whole car. Always make it the negative cable—or if you have a reason to need to pull both cables, like you need to replace the battery, always pull the negative cable first, before pulling the positive cable. Conversely, always install the negative cable last, after installing the positive cable.

The reason why: If you disconnect the positive battery cable first, you're putting a wrench on a terminal that is hot with respect to virtually every piece of metal within wrench-length's reach. Swing the wrench too far, drop the wrench, sneeze and jerk the wrench, and you're looking at hundreds of amps flowing through the wrench in a big hurry. The wrench will quickly weld itself in place, your hand can turn into a handburger, and you can have a real emergency on your hands in a couple blinks of an eye.

If you disconnect the negative cable first, you only have to worry about the location of the wrench relative to the positive battery terminal. All other metal in the vicinity is in common with the ground terminal, so even if you misplace the wrench, nothing bad will happen. This is worth considering when installing the battery cable terminals: Try and clock them such that when you put a wrench on the negative terminal clamp nut, it swings in an arc that does not move the other end of the wrench towards the positive terminal.