I'm close to the area of China that can't produce an 'R'. What's interesting is that the 'L' rather than the 'R' here (just East of Nanjing) loses clarity in words such as 'well' but is clear in 'Lily'.
Last summer I read about palatograms on free online accent reduction software. Palatography is a technique used to identify which parts of the mouth are used when making different sounds. In the pictures on the website, you can see the difference between the extent the tongue touches the palate for different sounds. It's more helpful than other diagrams. The site also has clear explanation videos by the Toronto linguist Rebecca of how to produce the sounds: accentschool.com/english_pronunciation_lessons.html
(scroll to the end of the software (tutorial) for the palatograms)
How to differ /l/ /n/ and /r/?
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