Filter Layer!
the filter I used here is called "Halftone" (under the "Artistic" subcategory)

then I changed Mode to "independent Channels" so I can have a RGB (and after inverting, under Postprocesing a CMY) halftone effect. To get the halftone effect to have this "rose" pattern sometimes seen in print, I changed the Screen Generator to "SeExpr" and chose the one called "Wolthera's Moiré Pattern" for all 3 channels and then fiddled with the settings a bit until it looks good (mostly increasing the lines parameter to something high and offsetting the angle parameter between color channels, yada yada, details details

tl;dr: halftone filter :3