I have been buying a season ticket to fish the Cambrian Angling Association waters for several years now as (a) it is very good value for money and (b) these are truly amazing wild places to fish which generally bring solitude, peace and quiet.
The links below are to articles that outline an adventure to these llyns/lakes which you will hopefully find informative and allow you to plan for a fishing trip to these waters and improve you chances of success.
Lower Llyn Du-bâch from the wall at the lower end of the lake 
Llyn y Manod 
Llyn Dubach y Bont 
Llyn Dwr Oer
Tight Lines
Greg