Thanks for the question.
In terms of finishing more quickly, you should familiarize yourself with the organizational template. I.e. the 5-paragraph format of intro-body-body-body-conclusion. You can slide any argument into that template if you practice enough.
In terms of writing a lot -- yes, writing more is most often better. Essay graders like to base at least of their scores on effort. And effort is perceived -- for better or worse -- on the quantity of text. This doesn't mean you should sacrifice time spent organizing your thoughts in order to write the Great American Novel, but do try to write as much as you responsibly can.
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