The spark plug boot/wire tools are pretty self explanatory. They pull on the boot rather than pulling the wire - and potentially pulling it out of the boot.
There are times that the battery post is smaller than normal - particularly if the terminal is taken off and put on multiple times it compresses the lead post. Then, when you get a new battery, the terminal won't open up to fit the new post. People will stick a screwdriver in the terminal to pry it open, but the tool is the proper way.