Well .... at least for me, I've found its very easy to round over and blur edges and you tend to end up with something that looks like a melted candle.
Rotary tools etc certainly do have their place, but if you use it for all the surfaces I find I'm not happy with the result. To get a true flat smooth surface requires either a surface grinder, or (the poor mans alternative ) Draw filing.
A tip for filing : Grind the edges of you file safe, meaning remove the file teeth so you can file right up against a shoulder and not remove material from where you don't intend to !