By making this Fireman helmet cake I bought a two pound tub of red fondant and used almost a full pound. I used boxed cake mix from the store for each layer but added an extra egg and spoon size scoop of sour cream to give it more body.
You can bake the cake itself in any size pan you see fit, I used an 11×15 sheet. while the cake is still warm out of the oven, use a plastic firemen helmet which fire stations give away most of the time when you take a tour. Wrap the inside with clear wrap (this will make it easier to get out).
What your basically going to do is grab chunks of the warm cake and press into the helmet to form the shape. I did three layers for the helmet and it is very messy when you involve the frosting.
Once you have all of your cake pressed into the helmet place in a larger bowl and use a towel for added support. I put it in the freezer for about 6-7 hours.
The shield I drew from scratch with a basic design and layed over a pitcher with wax paper.
Roll thin ropes of fondant to help with shaping underneath top layer of fondant. Then just layer and smooth. The brim of the helmet is fondant covered cardboard to support being on top of the bottom cake.