
I have Cairn terriers which I handstrip. I buy the rubber fingertip protectors that you can find in most stationary stores. They have little bumps on them which really help to grip the hair, as well as keep my finger from getting sore. I use the protector on my thumb and grip the hair between my thumb and the finger next to it. I have various stripping knives, chalk and other implements of torture :rolleyes:- but I've found the fingertip protectors the easiest of all. I'd recommend that unil you find someone who can teach you how to use it that you forgo buying a stripping knife. If it's used improperly it will cut hair, which defeats the purpose of hand stripping.
Handstripping means that you pull out the longest hairs of the top coat. In Cairns once the outer (course) hair has reached about two inches long it has stopped growing. For pet Cairns people either wait until all the coat has reached two inches and strip it all out at the same time. I roll my dogs' coats, which means a couple of times a month I pull all the longest hairs so the coat is always different lengths.
If you search the web I'm sure you can find a site dedicated to Westies for some breed-specific help (or Westie owners here) so that you "style" the hair correctly for the breed, especially the head, tail and skirt. At 3.5 months your puppy should just have lost her outer coat and will start growing her adult coat, so you have plenty of time if handstripping is for you.