The mini thing (SF call it) or hydraulic thing is the brake cylinder. Usually is the o ring inside the piston that fail or the rubber boot tear up that covers the piston internal. Adjusting is only needed if the linings have become thinner and the no. of click on your hand brake increase. For drum brakes users, your hand brake can roughly tell you how much your rear lining still have...more clicks mean the lining need to move further to come in contact with the hub. Usually 4 to 5 clicks is just nice....if 7 above, you need to check your rear lining for wear and if they are thick but they click is more then just readjust the lining against the hub via the back of the brake assembly.
The hub is made from cast iron so knocking it with a hammer won't dent it but would literally crack it into half or a chunk might just crack and broke away from the main piece. Best way to remove the hub, after removing the 2 philip screw with an impact screw driver, take a bolt that is the same size as the philips screw but with a much longer body drive it into the same hole where the philips screw was....this will force the hub to come out bit by bit until it totally come loose some cars drum will come with an empty bolt hole that's where you stick the bolt in. If you insist on using a hammer. try placing a piece of old rag over the hub. No need to hold the rag just totally cover the hub and slowly start to hammer it in a circular motion....you don't keep hitting the same spot over and over again. This will also make the hub come loose also.
For beginners, it might take a while but for seasoned guys, 10~15 mins can take out already.
If you plan on changing the lining yourself, well taking out the spring and fitting them back will be quite a challenge even for me...you will need some strong arm muscle and need to DIY a spring hook a strong one is a must so that it allow you to remove the 2 springs holding the lining together and then putting the spring back into the small opening on the lining base. This one needs patience to do and I swear you gonna sweat and keep cursing when you try to doing the spring....I know because I've did it....just be careful with the spring as it is very strong and most of the time it will fly quite far if it get loose from the spring removal tool. For safety wear a goggle. I kena my right eye brow before....bengkak and bleeding.
Happy trying...
