Applying underseal - fan-shaped spray pattern?

[threadlock]

At some point soon I'll be ready to apply some underseal to bits of my 1976 Stingray. I'll be trying to replicate as closely as possible the factory finish, which means a fan-shaped pattern from an air-fed nozzle. I'm sure they did it in this way for production line speed bearing in mind the careless approach of the factory workers.

Most videos I've found of people applying underseal show a fairly circular pattern, just like a paint nozzle on an aerosol.

Can anybody tell me where I can buy a spray gun for underseal that delivers a similarly wide fan-shaped spray? I'm guessing that paint nozzles (which seem to be available in fan-shaped tips) would clog with underseal.

[threadlock]

Thanks buzzer. How easy it to modify a spray nozzle given that I have no experience of using them (and no machine tools)? Is it something I could do with a needle file?