Lightweight Plaster w/o Perlite

Hi All,

I am just starting scenery and am in the process of hiding a track to staging.  

I made the cardboard matrix, covered it with heavy brown paper and then laid two layers of plaster cloth.  After curing, I wet it and put on a thick coat of Gypsolite.  I really don't like the  lumps of  Perlite.  After it cures, I will sand it smoother but is there a lightweight plaster product without Perlite that I can use for a thin coat over the plaster cloth?

Thanks,

Ed