Hi there
Just had a look at your question. Not sure if i can help but will try as i am starting a course soon in canine behaviour and dog training.
I have had a collie inthe past with dominance problems and agression and now i have a collie cross that's just plain nervous
Regards your grooming problems. A lot of dogs can feel threatened by a brush it can be worth investing in a grooming mit. Its basically a textured glove this way the dog can get used to the sensation of being groomed while not having the fear keep the brush insight and continue to let him see you groom your other dog this may in time build his confidence.
Regards your barking at strangers issue i think this is a collie trait the are territorial and essentially are guarding their flock so to speak. You may find distraction training a benefit this is when either with a rattle, training disc's pea's in a bottle or even a horn you make a noise just as the dog starts to react to the object that makes him bark as soon as the dogs attention is on you praise him and treat him. he should in time realise that barking at strangers isn't as rewarding as not barking at strangers
If you can introduce a clicker for training that will give you so much more help with rewarding the right moment the best website i can suggest and they have loads of books and dvd's from beginners to expert is
Learning About Dogs - Welcome
Take a look its a great method to basic training and behavoural training.
These dogs can become dominant if you let them they are very intelligent breed and can bore very easily but with all this in mind i'd have one every time.
Let me know how you get on i'm hoping to start my course and one-on-one training within the next year any feed back would be appreciated.