Even though it’s a little bit difficult to play the exercise slowly at first it’s important to get the proper technique. Pick up the speed little by little. If you find that your technique is starting to get off track it’s time to slow down again and work on it.
The other important aspect of practicing these exercises is to keep from getting really tense. Now it’s probably impossible to stay completely relaxed but you want to keep working at breaking the tension before it gets too bad. If you’re right hand gets really sore it’s time to take a little break and come back at it later