When do you count your hours for EtG? After the last beer or after alcahol would be out of your system?

Generally it is after your BAC returns to zero.

I got a no fail secret for passing a EtG/Ets test: Don't drink. It's the life hack that no one wants you to know about.

Seriously, don't try to cheat the system, it will win eventually. If you need help or support please look up AA or any of the hundred other support groups. There are people who can help you through this.