Long flexible plastic rod with barbs......run it down the drain to 'p' trap, twist it around and pull out the hair/gunk.
Works on sinks/showers.
That is provided the tank vents are clear and tanks are not full.
Get a flashlight and look real close at the drain. You will find it is coated with soap scum and hair. Everytime I have a drain that slows down there is stuff stuck to those small holes that are inside the drain pipe and just under it and further down stuck in the p-traps.