Create very long exposure clouds with brushes or other techniques in photoshop

Question

I know how to do long exposure, but sometimes, quite often in fact, the end result does not look as good as I wish, in terms of patterns.

An alternative would be replacing the sky, but I'm asking if it possible to create it from scratch. Assuming I'd like to create those very long exposure textures on the sky (essentially stripes of clouds like this), are there techniques (based on brushes?) to achieve that?

Essentially I want stripes of clouds like the image above. I searched online, but I could not find anything.

Answer 1

Photoshop have this nifty filter called "render>clouds". I use it for creating brushed metal textures and things like that but I think they could render some nice clouds.
But being sarcastic apart. When it come to realistic clouds I advise to use cloud brushes. You can download them from resource sites or create them by yourself (which is much easier). Just make a lot of sky photos with your camera set in a way you will replicate later (so angle, height above the ground, lens etc.) Then separate clouds and make brush from them.

Or just any brush and blur it like in above examples.

Remember, people will see in the picture what you tell them.

Answer 2

You could just use a blur effect. A radial blur is probably your best bet.

Take this:

Add a Radial Blur effect:

Mask the areas you don't want affected:

If the radial blur is too mechanical for your liking, you can add some distortion (Filter → Distort → Wave, Spherize or others). The dialog in the screenshot is left to show the effect magnitude.

Another quick example: