Does anyone out there have an old textbook about learning Moiyen Hakka?
There is a book entitled Dialect  and  Folkways  Handbook  in  Meizhou (梅州方言民俗图典) that you can purchase but it is probably more like a dictionary than anything else. 

Resources for, specifically, Moiyen (梅州) Hakka are going to be far more scarce than for a broader topic like the Hakka language in general.

Searching for Meixian (梅縣) Hakka would even greatly increase the number of results you get. 


现代汉语方言音库・梅县话音档
梅县客家方言志 
梅县方言词典