How to introduce a dog to wearing a muzzle?

[Kati]

I already have the muzzle. It fits her perfectly. It's made of leather and metal, so it isn't exactly light weight.
She will only be wearing it while we travel on the bus because dogs of her size must be muzzled on them.

I would prefer to hear from people that actually have experience with this rather than being redirected to websites. I'm also wondering if maybe getting a muzzle of a different material would help?
The muzzle won't be on her for longer than thirty minutes.
I've walked her with the muzzle on. She doesn't fight me putting it on her, but she walks strangely and has her head down when it's on. She immediately stops pawing at it when I tell her to. I just don't know how to get her used to it. That's why I'm wondering if it could be because it's too heavy?
The one she currently has looks similiar to this;
http://www.dogue-de-bordeaux-breed-store.com/images/large/Debordeaux-bulldog-wire-dog-muzzle_LRG.jpg
Sorry I didn't mention it, she is a Transylvanian Hound/APBT mix.