They say that 90% of writing is rewriting. But who trusts statistics? Sometimes, a project will prove such statements completely untrue, right?
It's more like 99%.
Personally, I quite enjoy it. It's an opportunity to make good scenes better; to sharpen dialogue to perfection. I get to polish that gold until it shines.
Getting notes on scenes you think are perfect can be hard - but you have to either make the requested changes, or convince the reader that their note is wrong. The latter should be done in the script, not in the meeting - there's clearly something missing to make them give you that note, and if you don't fix it, other people will have the same note further down the line.
Rewriting doesn't always involve polishing and editing what's already on the page. Sometimes, you're asked to do a "page one rewrite." Same idea, same characters, just do it differently - change the action, rethink the approach, throw out everything you've written and start completely fresh.
This is a lot harder to do as you're effectively writing a whole new script, not refining pages you already have - you're going to come out of it with another first draft. You have the difficult task of keeping the essence of what was there before while providing a whole load of new set pieces, scenes, characters, action...to make it feel like a fresh story they haven't seen before.
Whether you're working on a "band-aid pass" or a page-one rewrite, I've found the best way to work through notes is to break down what you're being asked to do. You're rarely lucky enough to have notes that spell it out simply - usually, you have to do a bit of digging and reading between the lines. Take their notes and analyze them - what are they really saying? What's the root of the problem, and how are you being asked to tackle it? Don't diverge too far from what you already have unless you're specifically asked to (again, find out why). Remember, you don't want to lose the magic that attracted them to the script in the first place.
Sometimes, a producer will suggest an idea for a specific plot or scene...but beware! Producers are not always creative people. Don't just regurgitate what they suggested straight onto the page. Find your own take - make it bigger, better, punchier, stronger, smarter, faster! The "bad producer version" is a template, an example of what they want; but it's your job to discover what's right for the script - again, deconstructing their example and stripping it down to the bones will help you understand what they're really asking for.
Getting notes is always a terrifying and exhilarating process. It means your job isn't done yet. There's more work to be done - but refining your script into something better is part of the fun, and it brings you a step closer to the end goal of seeing your project go into production.