Yep, Harry pretty much nailed it. I have a compressor and an airbrush, somewhere out in the garage...but I actually prefer using the Tamiya and Testors lacquer spray cans, mostly because I hate having to fire up the noisy compressor and clean the airbrush when I’m done...but that's all good conversation for another topic...
For brushed on paint, typically used for detailing small parts and features, I prefer the Tamiya acrylic paint in the small bottles. You can thin it with water or Isopropyl Alcohol (aka: IPA and rubbing alcohol). It's really great paint for kids because the smell isn't too bad and it can be cleaned with water or IPA when they spill it or get it on their hands.
For an 8yr old, I'd probably start him out with a snap kit. The advantage is they're easier and faster to build for impatient youngsters who want instant gratification. I’d also show him pictures of the in-process and finished models posted here on the forum.
Good luck,