You need to physically access the camera to make these changes via AP mode or WPS.
The camera must be placed in WPS or AP mode via its on board button. It would not be secure to have an AP mode constantly broadcasting.
From above the quote you referenced in the guide:
Connect a Wi-Fi capable device to the video device’s AP network
- Press and hold the WPS/Reset button on the back of the video device for 5 to 7 seconds until the LED starts flashing white.
- Using a computer, smartphone, or tablet, connect to the Wi-Fi network named ALARM (##:##:##) . The numbers in parentheses are the last six digits of the video device’s MAC address.
Without accessing the cameras physically, you could instead reconnect your old router, then after the cameras connect to it you can pre-emptively change the wireless credentials for the cameras manually in Alarm.com to whatever your new router is going to use.