How can I set a script that applies an alpha channel for each layer in the PSD file? An action makes it for one layer only. I`d like to have an ability to automate it for a bunch of layers.
What you probably want is a Photoshop Script instead which can allow you to apply an action to layers. Since you have an already recorded action you could use xtools to convert the action to a script. You might also have a look at their forums to see if your need has already been addressed with somebody elses' script.