Find right hashtags

I have trouble finding the right hastags for my Accounts

Everyone is telling me to find the right low volume hastags, i have no clue how to search for this.

Also how do you post your hashtags with massplanner? do you set up a big pool of relevant tags or handle them for each post individual?

Lets say your account is cats niche - in search bar write "#cats" then scroll down

oh man, now i feel kinda stupid.

anyways thnak you!