What is the correct way to use the Zerostat?

There is no correct way to use a Zerostat. The problem is once you start playing the record static builds up fast. The static charge is created by the stylus rubbing the groove. Even if you use a dust cover when you take the record back to it's sleeve it collects dust like a magnet. Hold a record you just played up to the light correctly and you can see the dust fly to the record. The only way to beat static electricity is to discharge the record while it is playing. So, if you don't want to stand over your record squeezing the trigger every 30 seconds the best solution is a conductive sweep arm like this one  https://www.sleevecityusa.com/Antistatic-Record-Cleaning-Arm-p/tac-01.htm. Also get rid of all your paper inner sleeves and get anti static plastic ones. Paper will hold a static charge.
Read about the triboelectric series here  https://www.school-for-champions.com/science/static_materials.htm#.XcFmJDNKiM8. You will notice that PVC is an electron magnet!

I bought a Zerostat in 1972 and still have it....albeit not used since the middle 80s. Back in the day I used the Zerostat and then lightly misted distilled water on the vinyl. Seemed quieter to me and it was fun.

After reading many threads here and elsewhere i have today taken delivery of a Milty ZeroStat brand new ...i hope it will see me out as i'm in my 50's

I saw a video showing the effectiveness of different methods using the  Zerostat gun earlier today.  I have had my Zerostat since the early 80s.  Seems I have been using it wrongly all of these years.  The new process that I have adopted seems to be very effective.  I reduced the surface noise on every record I listened to tonight significantly by using this new to me process.  And I have a VPI record cleaning machine.  Here is the trick:  Holding the record in one hand, point the Zerostat at the center of the record at a distance of about 8 inches.  Squeeze and release the trigger slowly so as not to allow the Zerostat to click.  Do three cycles of this and on the 4th cycle, squeeze the trigger and then point the gun away from the record and release the trigger slowly.  Now play and enjoy the record.  I use the Zerostat every time before playing a side.