There are two different concepts here: Watermarking and branding.
Watermarking is putting a big, obtrusive mark on the print that is intended to be difficult to remove and to prevent full enjoyment of the image.
In the hardcopy days, that was the big "PROOF" stamp across the front of the image. You do that when you're presenting an image for review and you don't want to deliver or sell that particular image to the client. You only want a selection and approval for a final product delivery.
Branding is identifying yourself or your studio as the creator of the image, but in a way that clearly visible, yet unobtrusive enough to allow full enjoyment of the image. This is like an artist signing his painting in the lower right corner, and it's done on an image you are presenting as the final product to the client.
I brand all of the consumer images I delive, both digital and hardcopy, with a stylized signature in the lower right corner, but you never want to brand commercial images (including TFP images for models and such).
So figure out which/when/how you want to do your branding and watermarking, but remember that they are two different concepts.