I don't think it's accurate to describe meditation as 'emptying your mind of all thoughts'.
At least not in my experience.
I could characterize it as a 'stillness'.
During meditation thoughts, feelings, sensations and insights can occur.
The trick, as it were, is to observe their fleeting presence yet remain grounded in the present, not to cling to them.
For me the premier goal of all my efforts is to know my Father and be pleasing in His sight.
Meditation, to me, can aid in that effort.
For one thing, being quiet reveals to me the tricks and illusions of my ego.
For another, it opens my mind and heart for my Father to enter.
While I find some encouragement for my course in scripture...
For example Luke 17:20-21, Matthew 6:33and Ps.46:10,
the real proof of the pudding is the intimacy of my relation to my Father.
It seems odd that you would indentify the 'cloud of unknowing' with Hinduism since it is a term of Christian literature.
I'm curious about 'Meditating on the law of God'.
I assume that it is a contemplation. A fertile spiritual technique.
But perhaps I misunderstand your meaning. Can you describe, meditating on the law of God?
Contemplatives describe meditating on the law of God as taking a short bit of scripture and saying it over and over...allowing a word to rise above the others until you are not thinking of anything at all. You are to empty your mind of everything, and enter into silence. The scripture is just a mantra to get you to "the cloud of unknowing." Better to study the Scripture so you can better understand it. Memorize it. But don't just use it as a mantra so you can have some sort of extra-biblical revelation.