Okay, here is my best guess on how to apply freckles, and keep in mind that it is an artistic way of spattering snow on to a painting, but I think the outcome would be the same.

In order for you to apply freckles in this way, whatever it is that you use needs to be liquid. I am racking my brains here to come up with something liquid that won't leave you with freckles for a week. I feel like I need to offer a disclaimer or something legal before I even suggest something I am thinking watered down acrylic paint - which would most likely leave a freckle residue for a week - or something like liquid eyeliner that isn't waterproof. the advantage to liquid acrylic is that it comes in a million different colors and should be easy to find at a store. It is pretty cheap, too. I don't know if you'd even be able to find liquid eyeliner in a redish-brown.

Okay, once you have something picked out to freckle yourself with, get a stiff toothbrush and dip it into the "paint" . Next use your fingernail or fingertip to scratch or rub the bottom of the brush so that it splatters the paint. Your might experiment on a piece of paper first and then somewhere like your leg next so that you can see if it is what you like.

Hope this works. My $ .02 for whatever it is worth.