Well I can tell you from experience because I groom dogs myself as a hobby, that it needs to be done properly, if done wrong it will hurt your dog and also mess up the coat but unless your planing on spending a few hours twice every year doing this then I can give you some tips. Ok firstly the dogs coat needs to be at least 3 to 4 inches long to grip the old hair especially if its been clipped previously. Theres two ways you can do this, either with your hand or with a stripping knife, the stripping knife is probably easier to use but the best way is to just do it by hand because you get a nicer finish than with the knife, its called a knife but its blunt with teeth that grip the dead hair and then you pull it out but I prefer to just pull it out by hand anyway. Start at the base of the tail grip the tips of hair with your two fingers and thumb but not the base of the hair because this is were new hair growth is. Then pull towards the way the coat grows thats towards the tail in case your not sure, don't be afraid to pull out the hair it will not hurt your dog as long as you pull the way the hair grows and not the other direction. Just repeat until you get to the eyebrows don't pluck them or the muzzle hair though. If there is any on the ears,cheeks and neck you can pluck them too and down the legs plus any stray untidy hairs on the tail can be plucked out too, afterwards you might want to brush the entire coat to get rid of any loose hair. Hope this made sense to you :)