From A Reyvateil's Wiki

Introduction

Here is the tutorial on the improved soft edges technique:

Note, this is based on the understanding that you have followed the previous tutorials.

I've already prepared the image using the techniques described in the previous tutorials, the soft edges have not been applied.

Guide

I'm going to start by applying the Select All command:

Click on the picture so that the selection is only on the graphics and not on the transparent region:

Apply a Select Selection Borders effect with Border Width set to 1, Both Sides, and Anti-Alias unchecked:

The selection should look something like this:

Now apply an Inside/Outside Feather effect with it set to Inside and by 1:

Clear the selection and Select None:

We're not finished yet.

Like before, choose to Select All and click on the picture so that it selects only the fully visible graphics.

Apply an Unfeather effect with Threshold set to 85:

Copy the image and create a New Raster Layer:

(Note, you have to do this separately for each graphics or it will copy the same face set to all of the pictures.)

On the new layer, apply another Inside/Outside Feather, the settings should be the same as last time:

Now apply a Paste Into Selection:

Turn off the older lower layers visibility, or just delete it, we have no more need for it:

Now create a Duplicate Layer:

And apply Merge Visible to the layers:

And that's that.

I would suggest creating a script in your graphics program so that you can apply it to different graphics.

On a side note, most of the time some touching up will still have to be applied:

The other tutorials should cover that.

Here are the finished graphics: