Follow every crypto related users. for sure they will always followback. that is the best way to boost twitter followers in a fast way. Also , do not forget to follow them back because if you dont , you will loose them sooner.
Addition, go to any bounty campaigns that has twitter campaign category, you can see all the twitter accounts there, follow them and for sure they will follow back since this bounty hunters need some followers too that may stick and will not unfollow. And additional suggestion, once you follow them but they don't follow back within 1-2 weeks then unfollow them 