Painting with brushes can be frustrating. The paint has to be thin enough to flow evenly, but thick enough to cover. You have to experiment, each brand of paint is different. Sometimes even paints of the same brand can vary, depending on how old the paint is. Older paint needs to be thinned more than a new bottle. The thinner in a bottle of paint will evaporate over time. Especially after the bottle has been opened. Even a 'new' bottle could have been sitting on the store shelf for a long time, and need to be thinned. Some colors are much harder to get good overage with on a large area. Silver, white, or yellow, for example. You might find it easier to use a spray can in some cases. The type of paint brush you use can also affect the finish. I find I get better results using short bristled, square tipped, paint brushes of different widths. Wider brushes for large areas and narrower ones for smaller parts. I hope I have helped you. Painting, like everything else, takes practice. After a while you will find what works best for you. Good luck, and keep at it. Al

first off if you are going to get serious about modeling (and i highly recommend it ...lol) invest in an airbrush. You can get a simple badger and a couple of the aircans to run it to make sure you like it. It makes painting larger areas a joy and the paint job looks marvelous.

As to what after spray. Depending on the model i use a spray can ot Testors dullcoat or glosscoat. Military models dullcoat cars and civilian planes glosscoat

Painting with a brush is always a personal way of finishing a model. You choose for enamels here whereas I would pick acrylic paint. Thinning the paint down and using several thin layers is generally a better modus operandi than whacking a thick layer down at once. Also for large areas I would always choose for an airbrush. Practice is always the best way to find which style suits yourself the best.
cheers,
Julian