Hi Frank,
So everything you asked happens to fall in the builders choice type of thing. Theres numerous products for each and most guys will find one they like and stick with it. Being the Polaris is your first ship I recommend trying trying different things/ways and use her not just to learn how to build a ship but also the supplies you like for yourself.
Varnish: I see many folks are using Tung Oil to get a great finish of the wood in a natural state. I also see guys using poly and minwax stains. Thats me so far but I will be trying Tung Oil on an upcoming build. My best advice : look around at furniture, find a finish you absolutely love then ask about its finish and try to replicate it. Any liquid can be thinned so yes you can airbrush all but the rub on type, however I see little reason to do so. Wood is pourus so the finish will seep in, unlike plastic.
Contact Cement: I would only use that for transferring paper frames to wood for precise cutting. It has it's uses and in translation sometimes contact cement is actually meant to be white glue. I myself use normal everyday Elmers wood glue. Many people love using the CA's or super glues, then others use Tite Bond ( unsure of the name, basically the same as pva but easier to fix goofs ).
Paints: Again, this is your choice. Any and all paints that can go on wood can go on your ship. Id say go with Acrylic simply because its water based to easy to clean your brushes and no fumes. If you are worried about brush strokes thin the paint just a little bit before painting. For a primer I prefer Kilz, yeah the same stuff you use for priming household stuff over stains and such.
Have fun with the Polaris, it's a very pretty ship