lacquer is the automotive eqivalent of varnish - it is a protective coat on top of the coloured base coat.
i would suggest to use plastic primer first, then base coat, then lacquer. all are available in cans.
lechler do a product called lechsys (i think) which will spray direct onto glass, plastic etc, i have used it in the past to make a red lens from a clear one.
i'm not sure if your local paint shop will load it into a can - might be worth asking though.