Who said "individually"?

Might want to check upon Photoshop´s docs for info on batch editing (With their ActionScripts). That way You just click and he does the rest ..

Sometimes they even use it to blur (Depth of Field) some rendered layers just in case the renderer didn´t do a good job ...

Now Of course Combustion or AfterEffects are better .. just saying it CAN be done in Photoshop.