I finally figured out how to use Cangjie to type Japanese! No, it's not the best way to input Japanese. It's slow and I won't recommend it to you unless you have plenty of time in your hands and little typing to do.
NOTE: It's not as slow as it looks in the video. My screen recorder consumes so much memory that it makes every other process crawl.
Cangjie and MOZC for Japanese
NOTE: The video quality is shabby. Blame Blogger for that! (~_^)
What I have done is no brainer. I have used two input systems - MOZC and Cangjie - simultaneously and I constantly toggle between them. A downside of this arrangement is that you are stuck if you have to type Roman characters.
I didn't do it out of laziness. I was trying to create my own ibus-table in the morning. After a couple of hours I had accomplished nothing. But, I had completely messed up my iBus so that all the input methods using tables just vanished. I had to reinstall.