I dig photographs with the streaky sky effect in it. It’s a pretty easy effect to do, it works best on a windy day when the clouds are hoofing by. You still want to have as slow a shutter speed as possible. Get yourself a remote that can hold your shutter open for longer than the standard 30 seconds available on most cameras. You only need one of the cheap ones with the button on it, not the fancy intervalomter kind. Put your camera on a sturdy platform, preferably a tripod. Set your camera to manual and bulb, leave your ISO as low as you can and press and hold the remote trigger. Remember to block out the viewfinder if using a DSLR, I usually hold my hand there or stand really close to the camera, I have got some strange thoughts when I do that. Once you’ve taken your first shot you’ll start to get an idea how long you’re going to have to hold the shutter open for. If it’s too dark you need to leave it open longer, too bright shorter, if your remote release doesn’t have a timer, use your watch or iphone, it’s not an exact science, just a bit of trial and error to get the desired effect.
This photo was 64 seconds at F9.