Possibly using fine silver foil would work for you. You need to
pierce the foil surface with a brass brush, tapping it all over the
shape, to eliminate the bubbles. Silver leaf is probably too thin
and could simply burn up in the kiln but it is cheaper and can
usually be bought one sheet at a time, should you want to try it.
Thompson Enamel is one source.
P.S. I didn't see a followup to the query about using hydrochloric
acid. Is anyone going to discuss using PnP and ferric chloride?
With a quantity of ammonia hanging around the corner for safety?