Do you need it to trim the hair, or everything but the hair? In the EZGS settings, the setting for non-hair defringe has the option to force contract by 1,2 or 3 pixels. This contracts the mask on the entire image. However, if you have hair refinement on, the hair gets refined after this. You can run this setting in batch.
If you want to do a 1 pix contract to everything, including the hair, then you will need to create your own action to do the photoshop steps manually. The EZGS touchup panel won’t record into an action. Action recordability for the Plugins menu was just introduced in PS 25, but the programmer has to program the plugins to record. I programmed this for the extraction button only. However, there is a huge limitation to this. The way Adobe made it, a plugin can’t play an action step that uses a plugin from the plugins panel. So the action would only ply back when clicking the button in the action panel, but not when running in batch from a plugin. Because of this current limitation set by Adobe, I decided to not waste my time programming the touchup buttons to be action recordable.
It’s a very simple action to make though with a few PS Steps. Record an action with these steps. This can then be attached to the bacth
1. Control+Click Windows or CMD+click for Mac on the Foreground mask to load as a selection
2. Invert the selection
3. Expand the Selection by 1 px
4. Select the foreground Layer Mask
5. Fill with black