Richard,

Sounds like the supply tube inside the can has separated from the nozzle at the top of the can.  Not normal.  I'd return it for an exchange.  Regarding sanding, it is almost impossible to sand Rustoleum.  But, if you let it cure for at least a week, you may be able to sand it to a smooth surface.  That will remove any runs you've got, but you will not be able to reclaim the shine.  The surface will have to be re-coated.

Paul