With Cloud Campaign you can choose default accounts. Anytime you create a new post or add content to your queue, the default accounts will be selected.
To set up your default accounts, go to your Brand Settings by clicking the gear icon in the top left corner of your screen
Under Linked Account, you can hover over the Settings icon next to each account and select Set as Default Account. Once it's selected, it will have the green "Default" icon added next to the account.
This quick hack will save you hours every month 🙌
Note: This will update default accounts for any new posts or added content, but will not retroactively update existing posts.