How to Add Motion Blur to Backgrounds in Photoshop
this video Aaron Nace from Phlearn demonstrates how to add motion blur for images with some movement in them.
The process here is pretty simple – you start by removing the subject from the background – just duplicate the background and use the spot healing brush to remove your subject. Convert the new layer to a smart object and now add motion blur to that clean layer (a path blur will also work in more complex cases).
The next step will be to use a layer mask to bring our subject back into the image. This can be very simple if you reduce the opacity of the new layer a bit so you can see the subject that you just removed. By adding a layer mask and painting black on your subject you re-introduce the subject (do this with a soft brush).
You can clean it up later on with some white brush but basically this is all to this – very simple and easy.