Street photography is one of the most difficult and time-intensive genres of photography, and you will realize that after going on one outing to shoot it. You have very little control and little time to react to shots forming around you, so mastering your settings is often crucial if you want to hit the shot. So, you would be reasonable to question why anyone would want to make it even harder by dragging the shutter with an ND filter.
In this video, go behind the scenes of a street photography outing with Frederik Trovatten in Hanoi where he uses an ND filter to force a slow shutter speed. There are a few takeaways from this video, for me at least, but perhaps the most resounding one is "confidence". You need to have the confidence to both miss shots and embrace the imperfections in shots you do get. Perhaps the subject will be soft or the background will be off-kilter — it doesn't matter.
So, if you want to make one of the most difficult genres of photography more difficult, give slow shutter speed street photography a whirl.
This is one of those techniques that is always extremely difficult to master and even more difficult to want to pull out of your bag of tricks when the opportunity arises.