Before sharpen:

After sharpen:

Thanks to Roxy for helping me test this action :)
The download link is after the cut. READ THE TUTORIAL BEFORE USING THE ACTION!
And I’ll update this post with a portuguese version tomorrow.
I know a lot of people (including myself) have problems sharpening gifs, because photoshop doesn’t allow to sharpen all layers at once… or at least I never found a solution. This PS Action isn’t perfect and doesn’t work just by pressing the play button, but it saves a lot of time as soon as you learn how to use it.
Here’s a gif of every step of the tutorial:

Here’s the tutorial:
So, after downloading and loading this action to photoshop, you’ll have something like this on the Actions Panel (default shortcut: Alt+F9):

My Action is called “Sharpen Gif Action”.
Import your video frames to layers. My Layers Panel looks like this:

As you can see I have 8 layers (which means I have 8 frames) and a group called “coloring”. Don’t pay attention to that group, it’s there because I prefer coloring before sharpening my gifs.
For this action to work you need to create a new group:

And place it between the “coloring” group and your layers like this:

Or if you don’t have a “coloring” group, move it on top of all the other layers.
Select all the layers of your gif (here I’ll select the 8 layers) and move them inside the “Group 1”, like this:

Now select the first frame and the first layer (or the visible/matching layer for that frame) like this:

First frame is selected, and the visible/matching layer of that frame is “Layer 5”.
Now there are a few thing you need to know before playing the action:
To play the action go to the Action Panel again. Select “Sharpen Gif Action” and click the play button:

A message will pop up, click “Continue”. Then a “Smart Sharpen” window will appear:

(I’m sorry if you don’t use “smart sharpen” to sharpen your gifs, but this is how I do it :/)
These numbers are random, so play around with it and see what looks best with your gif. Click “OK” when you’re done adjusting the settings.
After sharpening all the layers, the action will reach the group layer. And as you read before it will stop there because the group can’t be sharpened (once again, remember that the group can’t have a mask).
Finally, this message pops up:

Click “Stop” and you’re done! Your gif is sharpened! :)
TIP: To avoid problems, sharpen your gif as soon as you import your video frames to layers.
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I know that this may take some time to learn, probably as much time as it took me to figure out how to stop the action. But if you are used to sharpen your gifs layer by layer, learn how to do this and I assure you that you’ll save a lot of time ;)
And as I said at the beginning, this Action isn’t perfect but is useful to me and I thought I’d share it with you.
Enjoy :D