Hi - In reality this is quite a wide range of info and techniques, there are so many other more experienced modelers than me, hopefully they will ring in a bit here as well. My thoughts in the following order.
For enamel paint I don't always prime, although it could never hurt to do it anyway. Enamel paint and reducers seem to have enough plastic "bite" that it holds on to the plastic very well. I sometimes can get by with one coat of enamel, especially with "flat" paints, but they also allow a second coat within a couple of minutes. Gloss is another matter, I usually give a first coat about ten or more minutes in order to set up a bit, same for a third thin coat if necessary.
Acrylics I find a good bit more demanding, and there seems to be quite a definite characteristic difference between manufacturers. I always prime before spraying acrylics, it's really necessary if you plan to do any masking. Without a good primer coat, acrylics tend to lift off the painted surface when pulling off the tape. Acrylics are also more demanding as to thinning mediums, some are just not compatible with what another may work well with. Too much to try to list in this post, but you can just go through a few of the recent posts here, plus Google such as "How to spray Tamiya acrylics" or "How to thin Tamiya acrylics."
The best way I think is to just buy some of the type paint you intend to use, get their own product for thinning, (that's often the safest way,) then gather up a good supply of shiny, printed cardboard used for packaging everyday goods. Plain old cardboard or paper does not give you a good surface, for seeing the results of your work. Then practice, practice and practice some more. You'll soon see the way the thinning ratio works, how the spray pattern lays down, how smooth or rough the results are, etc.
You can also take a wing part before assembly, clean it well, then spray it for seeing results. Before the paint dries just clean it with thinner, you can repeat this as long as you need in order to feel confident to paint the whole model. Let us know how you make out, good luck with your efforts.
I don't recommend starting right off spraying a model, you might well be disappointed with your first attempt and turn out a job you're not happy with.
Patrick