Nice Project Using Old CDs. Supply list doesn't mention that you also need some pretty napkins or fabric.And where it says varnish I would use Mod Podge.
These are glass jars I (Annie Johnson) painted. I first sealed the jars with a smooth coat of sealer (Modge Podge or PVA thinned with water is fine), let it dry then basecoat with at least 3 coats of acrylic paint, then decorate with a design.