Being an enamelist, vitreous [glass] enamels are always my first
choice. That being said, I have been approached for repairs where
sometimes factors do not warrant traditional enamel. This may be
pieces that are soldered together or a costly [time intensive] repair
that the customer can not accept.
My solution has been colored nail polishes. They are very easy to
obtain and can be mixed with each other. Also, small bottles of model
paints offer a greater palette. Of course these “enamels” do not have
the hardness of glass but offer a glossy alternative.
One note, if thinning fingernail polishes be sure to use polish
thinner, not polish remover.