Tim,
My vote would also be for stain. It is not that I am against paint and love the old red barn look. In your case though, this wood was green less than 4 months ago and I would bet that a moisture meter would show that it is still wetter than you think. Moisture is a killer for a painted surface causing blistering and cracking. If it were to blister the rough sawed finish will make it real hard to prep in the future.
I would consider a transparent tinted stain, no surface layer to blister, for this fist go while the wood continues to cure. If a painted look is something you desire in the future you might want to use a water base rather than oil based stain. An oil-based stain can be a problem if over coated with latex paint in the next couple of years. Spraying is the only way to go and most stain manufactures recommend back brushing as you spray. Transparent stains are normally a wet on wet application if more than one coat is required.
MarkV