Begin your Photoshop filters by making a Merged Visible layer above all of your work to this point. This is a way of making a flattened copy of everything you see.

In order to make a new layer hit:
 Ctrl-Alt-Shift-E

Label the Merged Visible Layer by double-clicking its name in the Layers palette. Duplicate this Merged Visible Layer several times. The goal is to keep one Merged Visible Layer unfiltered, so only use filters on the ones that say “copy” in the name. Turn off all of the visibility eyes except the bottom Merged Visible Layer (the original) and the one right above it, which will become the first filter layer.

Apply a new Photoshop filter to this first filter layer. If it’s too pronounced, you can either use Fade (Edit > Fade) or you can just reduce that layer’s opacity. You can also change the layer’s blending mode, which marries the effect you just made with the layers below it (the Merged Visible Layer). Once you get this layer to your liking, label it with what you’ve done to it. Ideally you would put in the settings for the filter, especially if they are important to the result.

If you don’t remember your settings (and who does?) use Alt-Ctrl-F. This will bring back your last filter’s dialog box on your Photoshop. Remember those numbers and then click Cancel. If you want to add another filter effect, drag the next Merged Visible copy up to the top of the stack. Apply your filter and then use opacity or a blending mode to marry this with the effect you got before.

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