I think it's a great idea to do practice that way. Now that you have done it a couple of times, up your game a bit. Throw on some shaving cream and try it.

You might be surprised to see some of the area's that you miss. This is kind of important because it's those area's that you'll inevitably use more pressure to get to or at. If you use a dull blade to practice and focus on not using pressure, when you hit a spot that you didn't get all the cream - try using a different angle rather than pushing down on the blade. It'll pay huge dividends later!!

Good luck!