Four quick steps, about 12 minutes total. You'll never share a password, and you can remove my access any time.
You can disconnect any account from the same page, any time.
LinkedIn doesn't let anyone post on a personal profile except its owner. There's no helper setting like Facebook has. So there are two ways to do it.
I create each LinkedIn post and upload everything to a shared Google Drive folder: the caption, plus the photos or video. When you have a minute, open the folder, copy the caption and post it. About 1 minute a post.
A LinkedIn Page is a business page, separate from your profile. Pages can add helpers, so I can post there directly.
Every account stays in your name, with your login and your billing.
Never send me a password or a security code.
You can remove my access from the same screen at any time.