. All that being said, model painting is not so much an art, but it does require understand painting and drying process and what needs to be done for every different paint, both brand and types of paint. I have been painting most of my G scale models with the Rust-Oleum X2 paints and with great results, plus I also use the Testors in the Blue/White spray cans sold at hobby shops and Hobby Lobby. I do use the Testors clears and dull coats for my final coats and that even over the Rust-Oleum X2 paints. I still use my airbrush for colors that I can't find in those paints I listed above, but I only spray with enamels and acrylic lacquers, no water acrylics paint that stuff is junk for model painting.
I normally only use primers on models that I have done work on the plastic bodies, if it just a repaint no primes is needed, metal parts I would primes for sure. First thing I do is only paint when the weather is nice and no wind as I paint all models outside, I hold the model in one hand and the other the spray can, this way I can rotate both the model and the spray can so I can see how the paint is going on, the outside light pays a big .part here and putting the model in the correct angle lets you see if the paint being applies is too thick, or to thin. Most of my models are painted in 2-3 coats, a thin tack coat, a heavier second coat, and a third coat if needed, with each coat looked at from a side angle, this tells you if your coat is going on even or now, too wet, or too thin. There is only about 10 min. per coat drying time, or should I say a tack dry time, at this time my model painted, it goes on the shelf for 24 hours and at that time it's ready for decals, or the final clear, or dull coat which ever you want as a finish product.
Many modelers think the more coats of paint the better, or more coats make the model look better, in most cases both are wrong, you want the least amount paint, just enough to cover, thick paint on models serves no purpose as we are looking not to cover up detail, but to show off all our work. A ideal sprayed model would be one with wet thin coats, this is going to take some practice as wet coats are pretty much getting ready to create runs and then you have a big mess to deal with and your painting just got several days longer. I always tell modelers that are not getting good results with there painting that they need to practice on some models, old plastic model cars work great and learn to apply paints before painting you model that you have spend many hours on and it getting messed up do to bad paint practices. I pretty much wonder why in a day or so you are putting more paint on and then you get cracking, etc., well yes you probably with have problems as these paints are not dry, it take months for this to happen, don't read what the can says, the old rule of thumbs is, if you can smell it, it's not dry. If anyone wants to contact me through this website they can, I will try to answer there question if I can.
trainman