Paint and Priming help

Project 1:  I also use exclusively Tamiya acrylic paint and my store does not keep the flat base in stock neither.  So I use Testors dull coat in spray can for the final touch and it works good.

Project 2:  I know several modelers think that even if the real thing has a semi-gloss finish, it should more be flat that semi-gloss for a scale model because of the scale.  If you look at a plane from far distances, it will look more flat that gloss simply, so I always use flat coat.  Specially for war birds, I can hardly imagine them glossy since it could easily reflect the sun and be detected. Also, I noticed that the Testors dull coat I use doesn't have a totally flat finish, it's still got a little bit of shine, just enough for realism.  (My 2 cents)

Project 3:  I never saw a bottle of acrylic primer from Tamiya and I personnally use spray cans.  You can find cheap Krylon primers in any Home depot and it works perfectly.  And you could always spray the paint in another bottle and then use it with your airbrush, someone here use this technique to use the paint from the spray cans.  What is important is to spray the paint into a bottle with a small opening so the fumes and paint remains in the bottle.  The result is a perfectly thinned paint ready to airbrush.

Project 1:  What I use for flat coats is a mixture of Future and Tamiya X-21 Flat Base mixed at a ratio of 4 parts Future to 1 part Flat Base.  PolyScale also makes a clear flat that is often recommended.

Project 2:  Ditto Yann's comments.

Project 3:  I've never bothered with primer myself.  Even on a Panther tank that I painted with Tamiya acrylics, I just painted on bare plastic and found tha the paint adhered well enough.  If I was going to prime, I would probably be more likely to do so if I was painting acrylic instead of enamel or if I had done major surgery so that the kit was a hodgepodge of different colored plastics and putties. 

In regards to Project 1, the best flat I've found is Pollyscale Clear Flat.  It gives about the deadest flat out there, and no mixing is involved.  The most you need to add to it for airbrushing is a bit of distilled water.

In regards to Project 3, there are a lot of good primers out there but I airbrush Mr. Surfacer 1000.  It comes in spray cans too, but I've never felt comfortable using spray cans since you have so little control.  Some people don't use a primer, but I've found that it allows me to detect any flaws.  One reason I prefer Mr. Surfacer is because it fills those small defects and scratches.  I paint mainly with enamels, and from what I hear of those who paint with acrylics (which you do) is that a good primer coat can be critical for the paint to bond well to the surface of the model.

Hope this helps,

Mark