How do you propeely pronounce the French 'R'?

I can easily do the Spanish trilled 'R' and the English one, but I just can't do the throaty French 'R' properly in sentence. It comes the throat, yet it trills, but not in the same way the Spanish one does. For me, French isn't necessarily hard to speak other than that.
How do you propeely pronounce the French 'R'?
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