I justed started looking at stereograms. If you search Google for "stereograms" and then your can practice on those. I just pretend that whatever book I'm PRing is a stereogram. Just took a few hours to break the habit of cross-eyed PRing. And after you get into a rythm the words do become clearer. Which I kinda don't like cause it tempts me to read them so I always PR upside down and backwards. Hope that helps.
-Will
