My Dexter brakes have two plugs in the 6oclock position on the backing plate. There's a star wheel behind one of them (which one depends on which side of the axle faces forward).
I suggest that if you are adjusting your brakes you also check your wheel bearings. At least check the end play if you aren't going to remove the drums to check the races. I found that mine were getting quite a bit of play in them, enough that one of the grease seals had failed, filling the brake drum and shoes with grease and ruining the shoes. The bearings were fine, but if you are slinging grease into the brakes no amount of adjustment is going to give you the braking power you need, and greasy brake shoes also tend to stick.
If you gone through more than one brake adjustment without pulling the drums, I suggest pulling the drums and checking the magnets, which also wear. The magnet is what actuates the brakes, by pulling itself against the rotating brake drum and pushing the shoes outward through a lever and cam. So, it has friction material on it too. I was really surprised at how much brake dust was in my brakes with about 8k miles on them. They don't really self dump, there aren't any vents. So, bottom line is, if you can, pull the drums before you adjust the brakes and check it all out. That way you can also see where to stick the spoon in to adjust the star wheel.