painting

Total noob here. I was at a flea market over the weekend and bought a few brass interurban models (probably from the 1970s). To say the paint is bad is quite the understatement. What would be a good resource to use in learning this skill? Louise

I have been refurbishing some ancient but still salvagable freight cars. Several have great, unique decals. However I need to airbrush paint the cars. How can I preserve the old decal signage. If I mask it, it will look as if the signs have different paint behind them.:confused:

Pump Oil, easy to construct, with simple materials.