no no no... grab the airbrush (or paintbrush or whatever) and set it's mode to 'dissolve.' that will make it paint these godawful 8-bit airbrush dots all over the place. use the opacity to control the dot density. wave it over the area where you want freckles. this is good for making short fur, grass, snow... and freckles. you'll want to make them on a separate layer, probably, then run a slight gaussian blur on them. if they aren't big enough, paint a swatch on a layer, then size it up with the layer transform options. you can do a buncha layers of different sizes, merge them, blur them to taste, then use the clone tool to 'stamp' freckle patterns from it to wherever you want.