You yourself should NEVER INVOKE the cursing/negative energy.
Curse = negative energy!
You should EVOKE them instead, but not even in to your aura, okay?
Here read this link, it is very informative and easily explained. If you cannot understand it, then it is obvious you are not ready.
Magickal Evocation and Invocation
When using a curse with a rosary, you should keep using the *same* rosary for curses, and *not* use that rosary for another spells. When using the rosary for cursing, the rosary builds up the very negative energy inside the rosary. Which means, the rosary itself contains the energy/power.
Every rosary has 9 beads that follows with a bigger bead. On the big bead, you make an affirmation, or you can choose to make the affirmations after you are done vibrating the *selected* word of power. May it be rune, sanskrit or a traditional word.
(I am not a pro about rosary and the beads, I may be wrong, as I don't use rosary, I use something else)
And yes, visualization is of good help, and a very good focus and concentration is essential. Because you don't want any backfires!
There are certain planetary alignments you HAVE to watch out for, because it can cause a backlash and make a total backfire on you. The universe works either for you or against you.
Check your natal chart and so on. *STUDY* about magick on JoS, there are very good information about all this, and I suggest that you do *not* cast any curses until you are sure that you are strong enough, have enough knowledge, experienced with meditation and so on. Ask your GD to guide you and too work with you.
HAIL SATAN!!!