Photoshop :: Editing 2 Layer Without Merging

I have been using Photoshop for over 4 years now and only recently have I been faced with something I wanted to do but dont know how to do: editing 2 layers at once.

I understand you can put 2 layers in a set or use the layer link option in the layers pallete, to essentially move 2 layers around the workspace at once. However, what is the solution for applying blur/dodge/burn/smudge type effects but having it take effect on 2 seperate layers.

I know that I could merge them together and this problem would be circumvented entirely but thats not what I want. I sitll want to have them seperate, once Im done. I also know there is a long process I could do of saving the selection of one layer, merging it with the other layer, applying changes and then using the saved selection to extract the content back onto a seperate layer again.