There's another, similar, gadget that I prefer cazlled the "Heartwatch Fat Skimmer". It looks like a large ladle and is made of transparent plastic. The upper edge of the ladle's bowl is serrated, and there is a trigger on the ladle's handle that opens a tiny drain at the bottom of the ladle.
You push it down into, say, a pot of soup until the liquid just starts to flow in over the serrations. This liquid will be all fat if you push it down carefully. Once the ladle is full, you pull it out of the pot and squeeze the trigger to let out any non-fat that got in (and settled to the bottom). Then you dispose of the fat.
In my experience, this does a better job of separating. And you can use it in a large container of liquid rather than moving that container bit by bit in to other style of separator.