A few thoughts
about
Reinforcement
English Shepherds are an intelligent breed that quickly learns what appears to please the humans in its life. This is both a good thing and a bad thing. It's great if you are trying to get through the basics of obedience, but it's bad if you are unconsciously telling your dog things you don't really mean to be telling it.
For example, a stranger may come to your home. Your dog growls at the stranger. Meaning well, you may try comforting the dog with, "That's alright, he won't hurt you." Without meaning to, you are probably reinforcing your dog's aggressive behavior by your words and tone of voice.
Or your dog may paw at you for attention and you ruffle his head and talk encouragingly before returning to your duties. Or your dog may snap at another dog and you sensibly enough call him over to your side and put a reassuring hand on his collar. Or even, your dog may growl at you - when you grab his collar, or brush out some burrs, or reach for that pork chop you dropped on the floor - and you may ignore it ("I startled him", "It must hurt", "It's only a dirty old pork chop").
It's pretty easy to see what sort of wrong things your dog is quickly learning in these examples but we all do things like this every day. We forget that our dogs don't understand the words we speak, we forget that dogs live their lives within a "pack structure", and we forget that our dogs live in a very different world than ours.
Your dog needs you to be the pack leader and tell him (or her) how to behave. Your dog needs you to set limits, your dog needs you to say "no" when it is appropriate. "No, don't growl at the UPS man. Sit.", "No, that's my pork chop you silly old dog you. Sit." Say "no" like you mean it and make sure your dog sits and behaves.
Remember, you are in charge. You may have startled him when you grabbed his collar but as Alpha you have the right to grab his collar. You don't want to be mean, you don't want to make a big deal about it - but you do want to make sure that your dog remembers you are the top dog. If your dog really hates being brushed and resists getting the burrs out, then start brushing a non-confrontational spot, a spot without burrs and work up to the really bad places. Brush only for a short time and reward your dog with lots of praise and treats for being so stoic. Then do it some more in an hour and repeat till all the burrs are out.
The important thing is that in every case you have found a way (using your
superior human abilities to reason) to reinforce to your dog that you are
in charge and just what is acceptable behavior. If you and your dog
sometimes disagree about this point find times when you can practice
simple things you can agree on. Reinforcement works here too, and daily
reminders will make all the difference when you and your dog are staring
eye to eye over that pork chop.