There’s different methods used to output multichannel Photoshop color separations to film. If whatever you’re doing now works, stick with it. The PDF files below however might be helpful, especially for those newer to high-end color separation and film output.
For those using a newer version of Photoshop such as CS5, CS6 or Creative Cloud, I highly recommend using Illustrator or CorelDraw to print from as Adobe has removed the function from newer Photoshop versions which permits the assignment of LPI, Angle and Dot Shape for each channel. This is the reason why PDF’s are not available that cover the output of halftone films directly from newer Photoshop version as using Illustrator or CorelDraw is preferred.
It is possible to print halftone separations to film directly using newer versions of Photoshop although the films will be processed using the presets of your RIP and can’t be changed or overridden through the print functions of Photoshop.