I did mine, about 200' of mainline and perhaps half as much again of sidings, with a brush. I used PollyScale paint, straight from the bottle, and a fairly stiff 1/4" brush. The stiff brush allows you to get the paint around the moulded-on spike heads on the ties. Don't "dab": it's rough on the brush, and wastes time, too.

Turnouts take a little longer, but plain track is quick and easy, and you don't have to do the whole layout all at the same time. I do 10' or 12', then wipe the tops of the rails with a dry rag (the paint is dry to the touch, but not hardened, so it wipes off easily). Let it harden overnight before running trains. Don't worry about getting paint on the ties, either, as they get discoloured from the rails, too, on the prototype. I wouldn't spray paint in the layout room unless there was no other way to do the job: this is a good way to get paint dust on everything, and it'll all end up on the wheels of your trains, eventually.

:lol: :-D
Here are some prototype photos, for inspiration:
Wayne