If your going for the satin look as you say you can pull it off with a pretty small air source since you can do a little wait and do a little more and your not trying to get a full wet coat on the whole thing at once . The only time you need big air is when clear coating ..
One of the medium qulity guns you see posted as purple HF would be the right choice for now.
With the coaches we have here 24/7
all will be well
Got any pics of the project?