The best way to improve your in-exam time-management would be to just make sure you know your analyses like the back of your hand so that you don't have to spend time struggling to recall quotes and such! My friends use flashcards to do this ("Body Paragraph 2 analysis 2", etc), and then write them out as fast as they can, but whatever works for you, works! The next best way is to ensure that your essays actually can be written by you in the amount of time you will be given. Read through your essay and cut out anything you believe is bloating it too much. The third best way is to ensure you get enough sleep on the days leading up to and especially on the day of the HSC, and that you're in a good headspace so that you can perform at your best.
To practise at home, I just practise adapting each essay to a question and timing myself to see how long it'd take (I recommend setting a timer 5-minutes shorter than the time you'd ideally take to write it in the exam). You can also try to write & adapt all of your essays consecutively under the exact exam conditions once you've done that. But it really depends on what works for you!
It's fine if you have some time left over in the exam, and it's much better than having not finished! If you have some time, you might as well glance over your essay a bit. You might even catch yourself having skipped over a word by accident, or missing some words that could enhance the sound of your writing. I often have issues with my handwriting legibility (I write in cursive as a bad habit) so I tend to go through and rewrite words that I believe could be hard to read haha ^^!
And also, good luck!!!
