Film positives for screen printing can be print with RIP and with no RIP from Photoshop. I believe each channel separation is converted to a spot color and the next step is to convert the channels into a bitmap tiff, which is then out putted to separations from Photoshop. The above video's cover printing film positives separations from Photoshop without the need of dedicated RIP software.
Rip Software for printing film positives for screen printing isn't always necessary- but we do recommend using a RIP to print your color separations. It also covers the minor differences between newer and older Photoshop versions when printing films and covers printing solid spot color and index separations.