I am not sure whether you are aware of this technique. But is common to follow back someone who chose to follow you on Twitter. A lot of people do this. This helps a lot in increasing the number of followers.
Don't mistake this to be spammy, even serious accounts do follow back . Have you tried ?
Abhi yes. You can see the results of my Twitter feed by searching for @phenomlab
I am sure there are some big names on the followers' list. Good luck with your social endeavours.
Some people specifically ask you. I have followed you, you are obliged to follow me back.
I had one account where a lot of people followed me for a follow back. I got good no. in terms for followers and following. That project got me traffic too.
I think trying on Instagram helps too. Not sure as I haven't tried yet.