IMPORTANT : You have to manually set your PC's IP address to be
since your router's DHCP should not work at all.
You are correct, during power up/startup, some routers possibly will pause for a few seconds to accept a temporary firmware upload via tftp. However, some routers, after failed ROM flashing, may not pause at all.
If there is no response at all ( you can try a few times to ensure), you may not possibly flash anything to the bricked router. Then you may have to debrick with serial cable approach..