When you edit other people, go to their desk and sit down with them. Start by telling them what they did right. After the praise, go through your edits one by one. Cite the principle behind why you made the change.
If you only send the redline, the person you're editing will click "accept" on all of them and learn nothing. You'll make the same edits next time.
Every time you edit is an opportunity to teach. When someone learns to write better, that's time you get back.
WIN THE DEBATE, PART XVI. When someone says that this or that is the "most" or "best" or "greatest" or "weakest," ask them this question: What was the most or best or greatest before?
They'll rarely have an answer because we typically use superlatives (e.g. most, best, etc) for emphasis, not as fact. When you ask someone what their latest "best" replaces and they can't answer, you reveal that your opponent is offering not fact but opinion. This undercuts their authority and gives you an opening to return to fact.
(If they have a fact-based answer, fine. All you've done is make them back it up. That helps you, too, by keeping the argument in the realm of fact.)
Don't say, "I think this is caused by three things." Say, "This is caused by three things."
Feel the difference?
It's understood that this is your opinion. No need to underline it. As readers and listeners, we give more serious consideration to things said in confidence. "I think" and "maybe" and "perhaps" subtly diminish your authority.
Write for time goals, not words or pages. Set a timer for 20 minutes and work hard for 20 minutes. Then take a break, go do something else, or do the cycle again. Knowing that you get to stop after 20 minutes will help you stay focused and productive.
Let's say you went to the gym and you asked your trainer, how long will we work? And your trainer said, "Until you're exhausted." Ugh.
When you sit down to work "all day," that's what you're doing to yourself. Use a timer. Get more done.
For each edit pass, edit for only one thing. For instance, do a pass to identify and get rid of adverbs. Then do a pass for readability. Next, a pass for overlong sentences. And so on.
If you see other errors, ignore them until it's "their turn." Address them only during a pass dedicated to that topic.
Why do it this way? Because if you edit for everything you see, you'll get a few hundred words in, then you'll start over to see how the revisions read, and you'll do that over and over. Thus you'll end up with what everybody ends up with, a document edited to death up front with insufficient attention to the rest.
Also: when you complete a focused pass, you get the satisfaction of completing a task. That helps you find the motivation to do more.