Try this:

Open a new message, long press the bar on top (with the word TO:), Input method, copy, paste, cut will show up. Press Input method, you can select Swype, Android or Huawei keyboard. For chinese input, Huawei keyboard offer 'pinyin' and handwritting.

For pinyin, when you type fa, both 发 & 發 will show up. 发 is given priority, I have to press the right arrow button to select 發.
For writing input, you can write either Simplified or Traditional Chinese, both are supported in the same message.

Actually, no need to install google pinyin/ sogou for me.