I believe most people will agree that neon lights have a certain effect, any way they are used. Sometimes they're there to convey a sense of tacky decay, lighting the dangers of a dark alley. At times, to paint a lonely motel with fear and mystery, in a way only an old blinking sign can. Or turn night into day with countless signs, crammed up so close to each other, the city takes its shape from them.
Painting neon lights with traditional media can be tricky, depending on the medium. But the point is to understand the basic idea that makes neon lights look like neon lights. Air brushing is the easiest and probably also the ideal way to create that effect. But if you want to add neon lights in your artwork and air brushing isn't an option then all you need to do is follow the same principal with a brush.
In this video I created an alcohol based background and did the neon effect with gouache paint. Acrylics would also work perfectly. So have a look, grab your brushes and fave fun!