the easiest way to do it, or at least the way i do it, is that I put all the textures into a folder, I zip the folder, then i upload that zipped folder to Mediafire and then I send the link to the buyer.
You could use somethig that you can share a image with 1 person like when you press the send a private messege to person then you could upload a image in there but i dont know if you can send images in pms