Shooting with an ND Filter?

[Ricochetrider]

I recently acquired a Fuji X Pro 2 and been having fun getting to know the camera, which came with a 35mm & 16 mm lenses.
 

The 35 has a variable-stop neutral density filter which I’ve not used at all. I’ve seen blurred linger exposure daylight shots made with these filters already but never used one myself.
 

This camera makes it pretty easy to shoot manually, simply adjust shutter speed, aperture and even ISO (to some smaller degree) until it “looks” right in camera… well that’s my short term take anyway.
 

But I want to play with this filter a bit, can someone give me some hints on how to use it? 

[AlanKlein]

I could see using this in bright sunlight at the lowest ISO which would overexpose the picture otherwise.   This can happen when shooting video as well.  For example, using the 180 degree application for video, If you're shooting at 30fps, you set the video shutter at 1/60 which may be too slow at the lowest ISO of let's say 100 for the bright light conditions.  So turning on the filter allows the camera to shoot at 1/60 and not over exposure the video.   You could have similar issues with still pictures although with stills, you can always choose a higher shutter speed.  

Doesn't the camera automatically adjust for exposure and exposure readings when the ND filter is used?  I'm not familiar with your particular camera.