Newbie here.  I'm making my nephew's first birthday cake-- two layers, 12x18x2 pan.  I've been reading up on heating cores, and it seems like people recommend using more than one for this size.  Problem is, I have two flower nails, and they are different sizes.  Should I still use both of them?  Or just use one in the center?

Also: I was going to butter/parchment/butter the bottom of the pan-- is there some other way I'm supposed to prep the pan before baking?

Thanks!
 

I never use heating cores on 12x18 cakes; but if you want to, I think one is enough.  If you wanted to use two, it doesn't matter if your flower nails are different sizes. 

I use wax paper at the bottom of my pans, I don't butter them or anything extra.  I do, however, use baking strips around the outside of the pan.   (thick cotton material soaked in cold water works fine.)   Attach the strip with binder clips near the corners of the pan. 

I have been making cakes since 1982.

I use three flower nails, right down the middle - length wise.