Spriting over isn't the same thing as editing though.
Say you're using something like Paint.NET (like I am) or Adobe Photoshop (which most people don't recommend, don't see why not). It's as simple as making a new layer, and then spriting it, using the other pose as reference. Then, when you're done with the sprite, take it and move it onto a different sheet. And bam, the original sprite is still intact on the previous sheet (provided you actually deleted the overlayer rather than flattening it). It's called a reference, not an edit.
We all had to start from somewhere.
This is exactly what a lot of new spriters need to realize, and it's most apparent on
Serio's CVBla board. Most of them are like, "Man, this is too hard. I give up." or "I'm no spriter, I can't do this." But they should realize, even
Jorge must've been like that at one point, and look at his stuff now. Hell, I've even seen
Serio's old work of that
Richter sheet above (which is outdated, by the way), and it wasn't too fancy.
But again, MMMT101 (long abbreviation), I'll gladly give this a shot.