The Collaborative International Dictionary of English v.0.48:

Slush \Slush\ (sl[u^]sh), v. t. [imp. & p. p. Slushed; p. pr.
   & vb. n. Slushing.]
   1. To smear with slush or grease; as, to slush a mast.
      [1913 Webster]

   2. To paint with a mixture of white lead and lime.
      [1913 Webster]