Those tiny holes in your ceiling are for sound dampening as I am told and comparing my bus to others will full metal roofing I believe it to be true. My entire ceiling is done with that stuff and it is awesome.
As it so happens I just painted the entire inside of my bus this past weekend. Took a ton of planning to figure out how to paint it but not fill the holes and get it looking right. Let me provide what I can.
First you need to buy the 64 oz HVLP Professional from Harbor Freight. There are other solutions but with the volume of what your painting, the angle you need to paint it, and flow... this is the best product for the money. I have a few HVLP guns now from figuring this out and this is the winner. You can spray this upside down or any which way all day.
64 oz. Professional HVLP Air Spray Gun Kit
You need a large compressor that can run air tools. Specifically I went with one from Home Depot that is a 20 gallon tall monster. Most reviews of this HVLP gun are from people who I believe used the gun incorrectly and gave it negative reviews (they over preasured the system). Using the instructions that are included, set the air compressor when fully open to about 45 psi. I did not adjust the regulator on the unit. Oh, clean the hell out of the gun kit cause it stinks to high hell and is oiled when shipped. Anyhow use the paint flow bar to adjust the flow of paint.
Now this particular gun as a spray fan of like 1 foot which seems large. I shot white gloss rustoleum from Home Depot cut 80/20 with accetone. The accetone helps the paint cure faster and worked awesome.
My bus is a 30 foot Amtran Genisis and it took 1 gallon to paint the ceiling and walls (not the walls under the windows). The final product was amazing and dried the next day. I picked up a gallon of accetone and a gallon of paint thiner for clean up. It took longer to clean the gun than paint.
I took out all of my windows, wiped down all of the walls with the paint thinner, and taped off the vents, lights, speakers and windows that didnt get removed. I then sprayed using the method above. I had to fill the tank regularly and had my wife doing this. I dont think I would have wanted to do that alone as the paint dried super fast.
All said and done it looks like it was done at the factory and couldnt be more pleased. First time using an HVLP gun but I did air brush as a kid so it wasn't bad.
*** Forgot to mention, if you still want to fill the holes you can still do this, just keep the gun in one spot for a bit longer and the holes will fill. I have about 20 where I paused moving due to a hose getting caught up and need to re-open them. Just dont thin your paint and it will be easy to fill them.***