It sounds as if you aren't stripping at the right time, or maybe not stripping correctly? ;) when 'blown' the coat should come out easily and will then look good for quite some time ;) Is your friend using a stripping knife? These can cut the coat rather than strip it ;) I use finger cots or rubber surgical gloves for hand stripping - it's a much better finish and easier on the dog (in my experience) ;)
However, not all terriers have a good strippable coat and I've found that using a Coat King gives good results on these, you must work in the same direction as the lie of the coat though ;) I've found it far better then clipping as it keeps the outer hairs long and the undercoat from building up. Clipping will result in ALL the hairs being the same length, losing the weather-proofing and resulting in an exploded cushion effect in a very short time ;)
Excellent stripping page for Borders
HereAnd how to tell when the coat is ready to strip
here