Electrostatic Painting of Windows on Building

I am renovating an old factory building with Steel Windows, full sprinkler system etc. I have explored various options to paint the windows since they haven't been painted since the 40's it doesn't look like. Most paint has gone, some lead flaking.
I expect to brush hard, was going to prime with a rust inhibitor, then spray. At this time I have looked at the No. 2 electrostatic gun for painting both the windows and sprinkler system to limit overspray, but this is a $10,000.00 start up cost.
The other option would possibly be powder coat? Anyway, no one in this area has done any exterior electrostatic painting. The theory seems sound, a good ground to the solid steel windows and paint.

If you have info or experience with this type of renovation on the windows, or comments, I would greatly appreciate them..

Dear Sir I have been painting with electrostatic #2 gun for thirty years in Jackson. I can tell you your start up cost for a #2 gun is half of what you stated.
I also will tell you when you get ready to prime and paint you need to use a epoxy primer tinted to your top coat. Then your top coat needs to be a urethane with UV inhibitors in it.