The answer is so simple: use Loomly. I've use it one day in a week, and no need to start the process every day.
Open Facebook - read all of "important" news and messages - one hour.
Open the FB business manager, find the account, log in, start posting, etc etc etc...
Open the Instagram, browse all the "important" and "interesting" contents . one hour.
Start posting on IG, find the pictures, ets, etc, etc...
Open Loomly - upload ALL the necessary medias in batch - in the calendar make the posts at the same time to all social media accounts - done...
It's save one day monthly - how much is Your daily income?