Since she is a pup, I would first start rubbing her gums with your fingers just to get her used to the process. Until you feel comfortable using a brush, try wrapping guaze around your finger and using it as a toothbrush.
I just brushed my 2's teeth tonight and I use a childs tooth brush. I think I'm going to go back to the doggie brush and use the small end. I think that the brushes I have may be too big for them. Mine are 3 and 4.
Good luck and congrats on your baby.
