You may message participants by 'spot' (shift, job, what they are bringing). First, on the Home Page, click on Organize, choose My SignUps, and click on the SignUp name. Then, follow this sequence:
1. Select in the blue navigation bar and choose the orange button
2. Choose "by Spot" in the left pull-down, then choose the spot title(s) in the right pull-down.
3. Compose your message - you can even include links to maps, documents and surveys - then Send.
NOTE: To send a message to selected participants across multiple SignUps or Group Pages, please choose Advanced Messaging from the My Tools Menu.