Fixing most watches involve two things, either a spanner wrench or a simple tool to pull the back out. Well, if you happen to replace those batteries on you expensive watch all the time and pay at least $10 to the watch repair shops, there’s a better way. You can learn how to make your own spanner wrench custom0-fitted to your watch so you can replace the batteries yourself. (There’s also a guide on how to make a plastic spanner wrench but probably don’t recommend (nor will it work) on watch backs)
I also replace the battery on my TokyoFlash watch couple days ago myself so I should have a howto on that real soon too.