First of all, I think the instructions from markbolin are awesome! I wish I had them when I was making my cake. Here is a link to the bulldog cake I did a few months ago - - -
I didn't have any instructions, so I just downloaded several different pictures of dogs to get an idea of the overall shape. Then I carved the cakes and filled them, buttercreamed, chilled, and carved a little more to get the shape I wanted.
It was built as three cakes (2 for the body and 1 for the head). The cakes are staggered, so the bottom cake starts at the left of the cakeboard and the head is quite a bit farther forward. I then staked the entire cake with a dowel rod to make sure the head would stay in place.
The nice thing about a bulldog is that its okay if your fondant has a few ripples in the face - - - just make them work to your advantage for the jowls. I covered the head and body separately with fondant. I opted to add a t shirt, but a fondant dog collar would would have also covered the seam nicely. I then airbrushed the dog before adding the t-shirt and eyes to avoid accidently spraying them.
I hope this helps! Have fun with your cake.