I agree that it is difficult to get targeted followers.
I have several Twitter accounts and when I started each one what I did was commit some time to it each day for a period of time, following a few people and re-tweeting their tweets to get their attention so that they would hopefully follow me. I never followed masses of people because that does not look natural. I rarely follow a Twitter member who has an unusually high "following" count compared to their followers.
Once I get the account rolling, then I try to post tweets regularly and I check in regularly to follow new followers. I am selective with who I follow to some degree: if their following/follower ratio is out of whack, I don't follow them; if I don't think their tweets are compatible with my target market, I don't follow them; if there is anything suspicious about their account (like a female photo but a male name, or vice versa), I don't follow them.
Also, I typically do not follow Twitter members who seem to only be promoting the sale of Twitter followers! Again, that is not a natural way to build followers and probably not a beneficial way.
Just some thoughts.