In most of our searches, we do not use IPC classification only because we consider that the possibility of miss-classification by Japanese patent examiners is quite high. We often use combination of IPC and FT and full text keywords. For example, if we find for power management for dynamic memory, we would use F-term classification with such search strings:
(5B024 AA01+ 5B024CA23+ 5B024CA00+ 5B024DA20).
Plus we would use wide IPC classes/full text keywords combination with search strings such as:
(G11C11? + G11B05?) x (電源+電池+パワー)
For classification search, we often use PATOLIS database. For full text search, we prefer NRI database considering the database functionality and precision. After the search, we combine the hits from PATOLIS and NRI, and use a tool to eliminate the repetitions.