Easy way - use choose("abc", "def", "ghi","jkl",....) to randomly select one of text messages.
You can add a text object HintText, and do something like this:
HintText set text to choose("abc", "def", "ghi","jkl")
Wait 5 seconds
HintText set text to ""
If you want your hint messages to not repeat or if you want to highlight letters on your board or something like that - this will require more work.