It's basically just another step in painting. Lay down the base coat and let dry. Then comes the hydro. There are a printed film designs that you can pick from. And there are a ton of them. The film gets later into a special tub of water and then activator is sprayed. Dip the object and remove. Then clear coat it.
The best part about it is it can have way more detail then airbrush and it's WAY less expensive. Also, it gets into every nook and curve or tiny spot on the part. I have a video of the grill being done. I'll try to find it.