What is the reason for backing off the adjuster 3 clicks after you feel a slight brake drag. Why wouldn't you just leave the clicker alone after you feel the drag.
That's a very good question and one I have put a lot of work and thought into.
First of all, when the brakes are not being applied, you don't want brake linings dragging. So you have to back off some just to get to that point.
And, I have discovered from trial and error, it actually helps you get better braking if the "top" ends of the shoes (back ends, in the case of the rear brakes) start out just a bit further away from the drum face surface than they would be simply "not dragging". It has to do with the geometry of the shoes and the actuators (wedge in front, cam in back) at each shoe.
If you back off too many clicks beyond 3 to 5 clicks, then the braking effectiveness starts to go down again, because that end of the shoes is now too far from the drum face.
It's a balance, between adjusting the clicker end of the shoe and the brake rod clevis end. If you take your time doing it, you can get some really screaming good braking on these cars.
And once the brake rod clevis end is correct, you should do all further adjustments at the clicker end to make up for normal wear.
But, having said that, I usually repeat the brake adjustment procedure after 50 to 100 miles of driving, after the shoes have seated nicely and worn in a touch (any high spots wear down). I'm not opposed to small changes to the clevis on the brake rod at that point, if it improves braking or to balance out pulling on a hard brake application.
After that, adjust with the screw clicker only.