What program are you using to make the art?
Most of the time I use an app called Pixel Studio.
It's neat because I can use it on pc and android. I really like the workflow in this one, but when I plan to animate something I use libresprite (which is basically aseprite but free?). You can animate in Pixel Studio, but I use a paperdoll system for my character sprites. I have extra layers for hair, arms, faces, clothing, legs etc. And libresprite gives you better control over layers and frames.
Pixel Studio, however, has a cool export feature that lets you directly upscale the image. I usually post my sprites here in 4x.
I use good old GIMP for a few simple touchups or some mirroring and stuff. But that's basically because the other two programs are still opened with some projects I don't want to close. I'm lazy.
When I do animations I just mirror the frames, but you have to do it frame by frame. In GIMP my selection tool is capped to 32x48 (the size of my sprites) and snaps to the grid (which is also 32x48). To be fair, I could just mirror the frame in godot, but that scares me somehow?
If you want to know anything else, I'm happy to talk about all this stuff, because I have no one in person who can relate 🫠