Our family often had lamb cakes made in the old cast iron mold. I have tried several recipes, as the one my mom used is lost. My best results are with a purchased pound cake mix. My mold must be laid down, the "face" side filled with batter, then the top, or back of the lamb is not top. I have the most trouble un-molding the nose of the lamb. Lots of PAM, etc., but still it's tough to get out. Let the cake cool, slide a knife around, and then stick the nose back on with a toothpick and lots of frosting if all else fails.
Decorate your lamb with any white frosting and then press on coconut. Tie a real satin ribbon around the neck and put easter grass or green dyed coconut around the base.
I'm not sure that an angel food cake would work. I have not tried it, but it would be awfully fluffy to try and unmold. I would like to hear how it works.