Exact key sequence to boot from USB

[ryan]

My T42 screen is completely dead. Rather than try the numerous GPU fixes, I want to use it as a Ubuntu server.

I have an unattended install USB ready, but obviously I don't know the exact keys to press. I need something like "wait 10 seconds, hit F8, wait, hit down arrow 2 times, hit enter." But I don't know exactly what it would be because I don't have a screen.

Please, help!