About getting your license, CCW, registration together BEFORE the LEO is at the car . . .
In LEO speak this constitutes "furtive movements." That's what they call it. Furtive movements are sufficient cause for the officer to draw his gun and take cover, order you out of the vehicle at gunpoint with your hands in the air.
LEO's get nervous about "furtive movments." They also check for "furtive movements" to JUSTIFY holding you at gunpoint, ordering you out of the vehicle, etc. When the issue comes up in court, "Why did you, Officer, draw your weapon during this traffic stop?"
The LEO merely has to reply, "I observed 'furtive movements' by the defendant." That covers his butt in the eyes of the law.
Furtive movement can be as little as unfastening your seat belt, setting the parking brake, putting the vehicle in "park." It certainly includes digging out your ID, and by gawd you don't want to dig in the glove box.
If he "thinks" you're trying to stash something, "furtive movements" provide legal "probable cause" for a search of the vehicle.
Best policy when pulled over is to stop the car, turn on the dome light, put your hands on the wheel and wait for further instruction. Skip rolling down the window until he/she is there to watch you.
If you're carrying, inform them that you're carrying and the location of the firearm(s) (Required in some states). THEN let the LEO decide what he/she wants to do next.
--"put the gun on the dash" . . . NEVER heard of such a thing. I'd never let someone go for their gun for any kind of purpose during a routine stop.
Best policy is not to get pulled over in the first place. When I'm carrying, I'm super carefull about being courteous and lawful.