How do I message all my clients at once with bulk messaging?

You can bulk message clients by using a saved message template and sending it to a client list/audience.

Basic workflow:

Create or choose a message template
Use an Email or SMS template depending on how you want to reach clients.
Templates let you reuse the same message and include client-specific merge fields like their name.
Go to your contacts/clients list
Filter or select the clients you want to message.
This could be all clients, a specific list, past hunters, leads, etc.
Select multiple clients
Use the bulk select option if you want everyone in the filtered list.
Choose the bulk message/send action
Pick the template you want to send.
Review the message before sending.
Send
Confirm the recipients and send the bulk email or SMS.

I went ahead and opened Message Templates so you can start by creating or editing the message you want to send.

Pick or build a template in Message Templates, filter your Contacts list down to the audience you want, select them in bulk, choose the bulk send action, and confirm — the same template can merge in each client's name.