It seems to me that the reason people don't like doing this task is that they're using the wrong tools and are trying to be too neat. You could airbrush if you wanted to, but unless your layout can be taken outdoors, you shouldn't be using solvent-based paints. That leaves water-based acrylics; not the most enjoyable stuff to spray and in my opinion, not as durable when thinned, nor do they offer coverage as opaque. On top of that, more work to clean the airbrush, and you'll have not only the problem of overspray, but also all of the air-borne dried paint will eventually settle on the rest of the layout. Turnouts should be even more of a treat.
If you're using a brush, pick one at least 1/4" wide, regardless of your modelling scale, with bristles that have some stiffness to them and that are not too long. Check out what's available at an art supply store, as most hobbyshop brushes are meant for finer painting. You need a brush that will hold a decent amount of paint, and that will allow you to work the paint in around the moulded spike heads and the various contours of the rail itself. I use PollyScale paints for this, as they cover well, dry to-the-touch quickly, and are very durable once fully cured. I also recommend that you paint before ballasting.
I usually paint the turnouts first, as they require a bit more care: you don't want to seize-up the movement of the points with excess paint, nor do you want to block the electrical continuity, especially if you rely solely on the points for current distribution. Other than that, slop it on. As I mentioned, track without turnouts is a snap: try to keep the majority of the paint on the rails, even if it gets on the top, but don't sweat it if you get it on the ties. Paint with a back-and-forth motion, and let the brush do the work. The stiffer bristles will carry the paint around the spike heads, and the larger brush will ensure an adequate supply of paint, so you're not having to constantly dip back into the bottle. The first turnout might take 10 minutes to do, but you'll get faster as you go. Plain track shouldn't take more than a minute or so, for every 3' to 5'. When you've covered 15' or so, use a dry rag over your fingertip to wipe the excess paint from the top of the rail. A good thing to remember when painting turnouts is that the area around the points (the part that moves) is usually quite greasy on the prototype. If you paint the roadbed under this area with some shade of black, then when you ballast, use cinders instead of gravel, you can get away with using less ballasting material and glue, and thereby have less chance of gumming up the moving parts.
Most of you have seen photos of my layout, so you have a rough idea of how much track is involved. I used less than three bottles of PollyScale paint to do the entire layout, and the time involved was an hour here and there: when it became tedious, I quit for the day. This is a good task to perform when you want to unwind after work, as it's both easy and mindless, plus you get almost instant results.:thumb:
Wayne