Do you have to want to hurt someone for the cruciatus curse to work

OK so the scene where Harry sees Voldemort making Draco toutur Rowel brings a few questions to my mind.

he felt the rage that did not belong to him posses his soul, saw a long room, only light by fire light, and the grate blond Death Eater on the floor,screaming and writhing, and a slighter figure standing over him, wand outstretched, while Harry spoke in a high, cold, merciless voice. "More, Rowel, or shall we end it and feed you to Nagini? Lord Voldemort is not sure he will forgive you this time...You called me back for this, to tell me Harry Potter has escaped again? Draco, give Rowel another taste of our displeasure... do it, or feel, my wrath yourself!" A log fell in the fire: flames reared, their light darting across a terrified, pointed white face-

I remember in the Order of the Phoenix Harry tires to do the cruciatus curse on Bellatrix, it doesn't work. She say this is because Harry doesn't mean it, he doesn't want to hurt he enough. If she's right about that (I'm sure she is)I don't see how Draco is managing to make to make Rowel writher and scream, because it is clear he doesn't want to be doing it. Also Harry was actually angry at Bellatrix and if his anger at her killing his godfather won't work... well you get my drift. I know Draco probably better at magic, but I feel Bellatrix is right, you really have to want them to hurt for it to work.

Next thing, Voldemort's having Draco do it why? Is he doing to upset Lucius, because that and lot of effort to go to, seeing as Voldemort is angry and he'd probably do a better job him self. Or is he trying to train himself a new solider, I mean the other ones are getting old.