Hi Jaysun_d7
No I haven't tried PR to study language so I will not be able to help you in this regard.
With regard to building your vocabulary, I can offer a suggestion or two. Try PhotoReading the Dictionary multiple times. Do give a break of one sleep cycle between your successive PhotoReading sessions. I mean you can try it doing once per day for 15-20 days. Others have definitely benefited from it and I think so will you.
IMHO, one of the side benefits of a reading habit is that over time your vocabulary gets enriched. So extending this logic further, when you PhotoRead lot many books you will get an enriched vocabulary pretty soon.
As far as good strategy of PR for writing an essay is concerned, I will recommend you to read the Chapter 11 titled "Use Synoptic Reading for Life Long Exploration" in your Photoreading book, which came along with the course. This Chapter deals with how to read multiple books on a subject and then collate the material to write an essay or a paper.
I hope I have been of some help to you.
God bless you.
Kind regards
Vaibhav Sharma
