Is there a "Triage for Dummies Civilians"?

Yes. First, call 911. Then, if their dead you move on to the next victim. If they look like their going to die from their injuries, you move on to the next. If they look like you can provide aid with what you got, you help them. If there is multiple people and you can do it, write down what you do to the victim and put it where a 1st Responder can see when they get there.

Yes this is cavalier, but its honest. You can't save everyone all the time, and you shouldn't treat outside your ability.

Sure is. Holler at the top of your lungs, like you're in charge, "Everyone that can walk, meet up over here!" Then point to some highly visible landmark.

Bam, you've just gotten your walking wounded out of the way. Everyone else is dead or actually hurt.

The START algorithm is based on "30-2-Can Do." If they're breathing over 30 breaths/min, have a capillary refill >2seconds, or can't follow commands, they're either red (high acuity) or dead. If they pass all 3, but weren't one of the folks that walked to the side of the road, they're intermediate. It's that easy.

The big thing about triage though, is that you keep doing it. Everyone seems to forget (or at least not mention when we discuss it here) that it's an ongoing process. You constantly re-triage based on ongoing medical/traumatic complaints, body's decompensating, resources changing, etc.

In a real world professionally-run event, there's usually one paramedic/EMT running each triage "center" and someone over them, someone coordinating ambulances/helos, someone being gopher, people under the triage "boss" doing the actual hands-on patient care... it's actually rather complex.