is there a way to mirror traditionally painted textures? So I modeled a sort of dragon character, unwrapped it and blocked in colors with texture paint.



I exported the UVs and blocked texture to one of my art softwares. I kinda hate blender's texture painting for when you want something with clean lines.

My question is, if I make edits in an image editing software, is there a way for the texture to be mirrored on the x axis once i re-import it? It would be difficult to get both sides exactly the same in an image editing program without straight up duplicating and mirroring every single piece by hand. That takes a while and it feels like something that would have a solution in blender. anyway, any answers would help.
I think you should look at doing your painting in Blender and then 'fixing' it in your external editor. Look at two things to help : The Curves panel, choose a brush curve that gets you a better paint stroke along with the stroke type set to Curve where you can set the points with ctrl-click and then enter key to stroke along the path. 
For Symmetry, your UVs don't need to be lying on top of each other in Blender since you can toggle the symmetry axis there to determine where your paint is mirrored despite your UV island arrangement.

If you must use the external paint then you will need to make your object's UV islands to coincide right and left on top of each other, but I think you might be better off trying the method I laid out here.