Have you summoned up the courage to ask a professor or an employer for a recommendation, only to have that person say, "Sure, send me a draft and I'll sign it?"
That happens a lot, mostly with professional recommenders, but sometimes too with professors. It puts applicants in quite a pickle.
Because it's so common, applicants often turn around and ask if we can help them with those recommendation drafts. The answer is no.
Any admissions officer I know at any legitimate graduate school would not consider that a real recommendation if the recommender has outsourced writing it to someone else, especially if he's outsourced it to the applicant. For ethical reasons, our consultants cannot help you work on your own recommendation letters, even if the recommender told you to write it yourself.
Effectively, what that recommender is asking you to do is no different than if you came to me and said, "Hey Anna, will you write my application essay for me? It will have my name on it, and of course I have to sign off on the content, but it would save me a lot of time." That wouldn't be considered ethical either, for reasons that I hope are obvious.
It is OK for you to have input in the recommendation letter (if the recommender invites that), and even to give your recommender feedback on a draft. It's fine to take your recommender out for coffee and talk about what the recommendation might cover (if the recommender would like that). But you can't do the drafting; it can't be you trying to emulate that person's voice or pretend to be writing as that person.
One solution, if the recommender is willing, would be for you to provide bullet points of things you'd like the letter to cover, with the understanding that ultimately it's the recommender's decision what does or doesn't end up in the letter. And the actual writing of the letter would still have to be done by the recommender. Shortcuts aren't OK, and delegating isn't OK.