So you want to import fallout's BOS armor into your game, by converting the spr to png?
I did an experiment like this a year ago, exactly around this time, but in july. I even made a thread about it months later
http://www.nma-fallout.com/threads/sprite-resizing.216762/
But I was resizing sprite instead.
And yes, you must export them from redviewer or jarekfall's sprite creator one at a time. That's why I abandoned sprite resizing for that omega power armor since there was no other program to do it fast. It would have took me one whole month to resize and export from spriteviewer just that sprite and make the character look like a 12ft (360 cm) giant.
Why do you all use unity anyways? It's a garbage engine or whatever it is, idk i didn't try it. Because it's some new thing that shouldn't exist, I heard about unity in 2014, I don't quite like it.
An action(standing, crouching) from a sprite consist of multiple frames oriented in all the 16 directions, or 4 depending on what you are up to. It's very hard, and takes time, I would tell you to look upon some .bat program to do it for you. I used adobe photoshop to resize the sprites, but I had programmed a batch automatic resizing. It's possible to program a robot on windows (aka .bat file) to do it for you.
You have to export the PNGs from the file manually, unless you come up with some .bat program.