I buy my intercoat clear from either House Of Kolor (SG-100), or from X-otic Colours (34-200). They are interchangeable.

It is a nice protective coat, which is simply basecoat resin without any pigment or color.

It will protect metallics from getting disturbed.... or solid colors, which can also be disturbed and have differences in color show up later.

Another use is to shoot a basecoated surface, before topcoating, if you have waited too long. The basecoat will stick and freshen the surface, so the topcoat can get max adhesion.