I'll just tell you what I did and see if it is of any use.
One end on the shop is open. I set the boat upside down supported by bricks under the beam landings so I could take down my winching system as it would get in the way.
I put planks on milk creates down both sides of the hull. This enabled me reach far enough to spray from the keel to the waterline on each side.
I did 3 passes. Alternating from side to side, always spraying from the back of the shop to 7ft x 8ft opening.
Then I took the planks away and 3 passes from the gunwale to the waterline. Same again. A friend came around and mixed while I sprayed in an effort to keep a wet edge. I expected to get over spray from the waterline to the keel but that didn't happen. The 2 pack paint I'm using stayed wet enough to absorb the over spray.
I had a 13cfm compressor driving my positive pressure full face mask and a 15cfm on the HPLV gun. When I undercoated I only used the 13cfm on both and I had to stop intermittently for the compressor to catch up.
I also have a very large fan that I could have used to help vent the shop had it been necessary.
That worked for me.
Hope it helps.
If you have too much mist in the air look at you pressure at the gun. Too much could do that. I did not have that problem. Overspray on the hull now will be avoided by taping plastic sheeting from just under the gunwale down to the cradle the hull is in. I have a heap of cheap plastic sheeting left over from when I made the cradle and it will only take a couple mins to tape in place.
This has all worked great for me with the paint I have chosen to use.