I came across this site while researching cast iron cake molds...

I have my grandmother's molds -- the rabbit and the lamb. She was a professional baker back in her day, so here are a few tips that she passed on to me (and some that I learned on my own):

1) Use cooking spray (PAM, etc) to thoroughly coat the top and bottom interiors. No need to dust with flour.

2) Use a heavy cake batter; I have a long-time family pound cake recipe that I always use.

3) Add extra batter in the ears; you might also want to insert a toothpick into each ear to help brace the area when you pop the cake out from the mold.

Good luck!