Learn to Quickly Cycle through Photoshop Layer Blend Modes
It's super simple just use Shift+
This is especially handy when using texture overlays and word art. Simply click on a layer in your layer palette then hit the + button while holding down your shift key.
Shift- will reverse the cycling of the blend modes.
One note, if you are using a tool that supports blend modes (like the brush tool) the shortcut will default to changing the blend mode of the tool, not the layer.