Originally Posted by
Moonshae
I'm not sure how useful practicing with a dull blade would be. You might learn a little bit about angles, but without the feedback of actual hair removal, you won't know if you're doing it right or learning bad habits, especially with regard to pressure. You're better off just starting with a properly sharp, shave ready blade and following Lynn's advice on how to start shaving with a straight.
It's actually pretty difficult to hurt yourself with a straight. Small nicks are not a big deal, and you'll likely be dealing with razor burn mostly at first. A dull blade won't help you avoid those.