Shih-Tsu's need a lot of brushing. Whether you have the classic look which is the long hair to the floor with a top knot or ponytail tied at the head, or you have your pets trimmed short like I do, you still need to keep on top of it.
Most people automatically think that the longer the hair, the more brushing the dog requires. But even with the short hair, you need to brush it often.
The longer hair in some respects may be a bit easier to maintain because the weight of the fur will keep it from getting too messy. With the shorter cut, I find the dogs can look messy if I don't brush them each day as the hair is more fly-away.
However, one of the most important reasons for constant brushing is to prevent matting. Any of us who have tried to get through a serious mat in our dog's fur knows that we swear to be more diligent at brushing to prevent this from ever happening again. However, mats do happen for different reasons depending on the dog's behavior. With mine, behind the ear is the most common place because when they want to play, that's where they nip at each other. And that's the first place I brush. You'll know you're own dog and where they are prone to mat. Typical areas are behind the ear, on the bum, the back of the legs and the beginning of the tail (we tend to brush the ends a lot to make it look fluffy, but it's the start of the tail that often gets neglected).
Because their fur is so thick, the brushing also helps clean it out and spreads the natural oils within the hair to keep it healthy. And because Shih-Tsu's don't shed like the average dog, the brushing helps release some of the excess hair and again, cleans out the fur.
You definitely need the flat wire brush for working through their thick, luxurious hair. I use it every day on the dogs. Don't try using a regular bristle brush...it'll will only smooth the surface and after a while the mats will build up underneath. I also use a comb regularly after the wire brush to make sure I haven't missed any major knots. I don't do this every day, but once a week is fine.
Although some may think of brushing as tedious, I use it as a way to bond with the boys. I started brushing them when they were puppies to get them used to the tools and now they come quite happily when I call them because it's their private time with "mom". I don't allow the other to interfere...I make sure that while I brush them I speak soothingly to them...and I pat them a lot as I'm brushing them as they find it very comforting.
Regular brushing is not an option with this breed - it's a necessity. However, it doesn't have to be fight. With the right tools and loving hands, you can make this an experience that you and your pets look forward to.