Caswell says their flash copper plating kits
may be used on bullets. See here for specifics of use
. A few hundred dollars to set up.
I don't know what the custom mold stuff is about unless you are determined to plate the bullets as-cast. Otherwise, just size them down a couple thousandths and clean the lube off before plating. A custom sizing die from Lee cost less than a custom mold. last time I looked.