dark to light...or light to dark??

I'm painting a friend's bulldog ( see attached ) in acrylic, and i'm wondering if there is a general rule for which tones to start off with. I've done a lot of online research and it seems to be a case of different strokes for different folks, which is annoying because I just want to know for sure! Going by the colours in the picture, what would you reccommend in this case-light to dark or dark to light? Does it depend on the subject? I would have thought it may be easier to add the shadows last rather than have to paint white over the top of a dark colour..but alas, your views are very much welcome! Thanks!