I've seen somewhere where normal consistency icing has been used to outline a section and then the icing is thinned and used to 'flood' the section. I'm not sure if that's making sense, but does anyone know how to do that?

I tried on one of my cakes and thinned the icing with water. It filled the section well enough, but weird white flecks of (I think!) Crisco floated to the top...

Any ideas? Thanks in advance!