DIY dog grooming. My dog is kinda mean, so I am being forced to do it myself?

Wow, it's like practically nobody read your question and just flung out all sort of opinions about mats and stuff you didn't even mention. Wierd. Also, about 95 % of pet Shih Tzus ARE clipped down into various length "Puppy Cuts".

Generally, clip the coat, wash the dog, dry the dog, reclip the coat. You may find that the dog bites you at the same point he bites the groomers, in which case you would have to resort to the vet grooming.

Places to watch your fingers and face are doing his feet and working around his face. Some males get nasty about having their privates shaved. If he is not neutered, I recommend you get him done. No sense to ever breed a Shih Tzu with a bad attitude, generally Shih Tzus are nice and calm, never mean.

If your grooming set can not handle his fur, go to a pet super store and buy an Andis clipper and get one that includes a #10 blade. Then you could buy a #4 blade on the side and you could clip him with that blade in the winter, the 10 in the summer.