Getting Chinese Tourist visa from Hong Kong or from Egypt? Required papers? Regular Processing time?

I've booked a flight to Hong Kong for tourism and booked my stay for 2 weeks but I'm planning to extend it if I liked the place. I wanted also to to visit China during my visit in South East Asia by taking a train from Hong Kong.
Should I apply for Chinese tourist L from Hong Kong or from Egypt?
Also what would be the required papers in this case?
And what's the processing time for the regular tourist L?