Ok.
First of all, with the airbrushes, I use Harder and Steinbeck Evolution Silverline. It is their mid range mairbrush and is sturdy, easy to look after with drop in nozzles. they have 0.15, 0.2, 0.4 &0.6 available and you can buy a silverline with 0.2 and 0.4 nozzles in the set.
You need to think about a budget for these purchases and I can recommend some retaillers if you are in the UK.
You will also need a compressor too!
Vallejo Model Air is not available on the Vallejo website to buy, but there are many online retailers that sell the stuff.
Here are my most recent builds from the Zouki-Mura range painted with Vallejo model air, Vallejo Metal Color and AK Xtreme Metal paint ranges and with the 0.4 nozzle.
Please give me chance to update my notes. I am away playing with my big toys this weekend!