Besides what everyone else already said, you'll always have to go through the work of blotting out the letters with the mouse every new time you do the RTR, no matter if you blot them out before doing the vibrations or during the process. So what you suggested just adds extra and unecessary work to it.
I don't know what your version of Windows/Paint is, but I always choose the Oil Brush, increase its size 10x, and blot out the letters in circular movements. That's the most efficient for me, since it takes just 2 or 3 circular movements to blot out each letter completely (at least on my laptop mouse pad).
On a side note, I have also tweaked the file to my liking: I've cut out the instructions for the vibrations, the affirmations and the Hail Satan part, leaving just the hebrew letters.
I did this because we have to delete the file in the end, and I'm a little paranoid with the idea of deleting the affirmations and the Hail Satan along with it. Imagine doing it physically, with the file printed out on paper. Defiling the paper and then throwing it away, and knowing you're doing that to the affirmations and to the Hail Satan, too. I wouldn't like to do that. I don't know if that makes a difference, but I preferred to cut out these parts, to have in mind that I'm deleting just the blotted out letters.
I used to follow the instructions for the vibrations on a separate file, but now I know them by heart. It gets much smoother and faster to perform this RTR when you remember the vibrations by heart. You can work up to that point by trying to remember the vibrations each time you perform the RTR. Vibrate those you remember, read those you don't. And so on, until you perform the RTR and you are able to remember all the vibrations. That's how I did it. But this is optional. What's more important is the main instructions given by Azazel.