Hello Ives:
<<You could give me some training advice?
Sure, do NOT drop the things... they hur your feet!

Sorry I couldn't resist....
Kusanku Sai
Chatanyara No Sai
Sai are a part of the curricilium but have not been reexamined in a long time. I like them but I would not pretend to have any bone fide expertise with them. Put them in your hands, a lot... flip them, twirl them, flip them....in time attempt to hit things with them, as you do with all basic empty handed techniques.
Once achieved play with other practitioners, the exploration will be enjoyable. In time increase the quality of the folks you work with...
Sai a wonderful weapon...
Jeff