Jim Johnston says:

I use an acrylic base wash… A little heavier in freight areas than on main lines and darkest of all in car storage and repair areas. Just use a piece of plastic card on the top rail surface and you’re good to go.

W Rusty Lane says:

I use an airbrush to paint the ties and track sides. Usually a rail brown color.

Morgan Bilbo says:

The easiest way I know of is to paint before laying. Place the flex and turnouts on newspaper. Mask the points. Use any good rattle can paint. Color of your choice. I chose a dark brown. Others have mentioned Camouflage Brown. Above mentioned grey. Wipe the rails before they dry with a piece of soft pine wood. Dries within an hour to handle/carefully. If track is already down, the best way is with a brush. Use a couple different colors and paint ties so they don’t look “uniform”. (And yes, it’s tedious.) Later, when you start to think about ballast. That’s the time to use markers, brushes, etc. and touch up ties separately. And the sides of rails. Again, if you get paint on top, wipe off immediately. An alternative is to spread an oil/vaseline with a finger and after done painting, clean like you normally do – with alcohol. The only time I ever use an abrasive is if the rails are so grimy that the alcohol don’t clean. Finally, my last step is very lightly wipe graphite on about an inch of rail, every foot or so and use cars to spread it. And after that, just keep running trains. The more you run, the less trouble.