Each Blynk project has its own unique authorization token. You can duplicate the same project for each garage door you have, and each of them will be assigned a different authorization token. On your first OG device, put the first token, and on your second device, put the second token. This way each device communicates with its specific Blynk project.
You can give each Blynk project a different name to help you distinguish them apart. To switch between different projects in Blynk, click the ‘exit-door’ like icon on the top-left corner, then you can swipe left and right to switch between different projects.