There i lots of criteria to choose the right bounty so you won't be wasting your time:
1 - Chose only SOLID & PROMISING ICO / Projects.
2 - Do as many bounties as you can (they are profitable if you're smart enough).

As for how to get Twitter followers, it's easy, just go check those Follow & follow back FREE websites to get fans, by the time you'll be having 10's of followers so easy, yes this take time but totally worth it.