It starts in the art department with a graphics artist. Anything from a resize, change in position, recolor, etc means the graphics artist has to modify it and get it ready to print onto film. Each color including bases are a seperate image. Each one of those is then printed onto a film which are then placed on the screen in the proper place. (This is done with measuring tools because each film has to be placed on exactly the same spot on their respective screens) Once that's done the screens are burned, films are removed, and the screens are washed, prepped, taped, and labeled. They are then taken to the presses and setup. If they need a flash, basically a high powered heat lamp to dry the ink between screens, that's setup in place of a screen. Ink goes in and they begin testing the print, so if you place a film even 1/16 in off they will find out here and that screen may have to go back to that step. Once the test prints are done they either take pictures for final approval from the buyer or you have to send out samples if the buyer wants to ensure color accuracy and such in person. This whole process can take up to half a day (sometimes more if there are issues or the superstar you are printing for is unreachable on their yacht) depending on complexity and amount of colors and it involves people from almost every department. The biggest thing with hoodies is the flash slows down the printing considerably as the flash takes longer than the screen to print. So let's say a tshirt takes 1 second to print per color and their are 5 colors, that's five seconds to print. Now for a hoodie it may be 1 second per screen but 1.5 per flash with as many flashes as screens, that's 12.5 seconds per shirt. (Somewhat of an oversimplification, but you get my point, hopefully) On the logistics side of things, hoodies are more expensive per piece to ship and store than tshirts from the printer.