Polyester moulds are the most common moulds in the industry, and not only for there price:
Polyester tooling gelcoat can be either brush or spray applyed using a gelcoat 'cup gun' and gives a remarkably hard surface that can be buffed to a brilliant shine.
Polyester resin sticks to itself better when wet, meaning your moulds dont require vacuum bagging, unlike epoxy resin which should be vacuum bagged to prevent voids in the backing and behind the mould face.
Use 1 layer of 225g chopped strand mat for the first layer after the tooling gelcoat. This helps prevent voids and fiber print through.
Use 450g chopped strand mat to build thickness in your backing.
The semi perm kit gives you either 150g or 3.8L each of: cleaner, sealer and release agent. It is easy to apply to your plug, and gives you an A-Class finish. (The surface of the plug needs to be compatible, i.e acrylic paint will not work) If you are unsure PVA and wax can be purchaced here and here (Follow the instructions provided to the letter, we know its tempting.. but do not take shortcuts!)