cake making

So I've been thinking that I might make Graham's birthday cake. Graham has been sick the last few days, so I decided that I was going to try and make my first fondant cake. Disregard that it's only one color (I didn't see the point in making two colors since this was just a test) and that there are stars on top (that's just a cookie cutter that I already had). What do you think? The only thing is I had a hard time rubbing in all of the powered sugar...you can see a few white flecks here and there. Any idea how to completely smooth out the cake and make sure you don't see any of that sugar?