In Twitter it is not so important to have thousands of followers. Numbers are never equal to conversion rates. It is much better if you build a followers list that is based on what you are promoting and your niche, and not just a simple list of many followers that are not properly targeted.
It is really worth to have smaller targeted followers better than to have 1k followers but they spammers
As others have stated, a better way is to get targeted followers by using keyword searchs of profiles and tweets. Also, for instance - with tweet adder you can filter tweets and remove those that include url's (more likely to be sellers) and those tweets from profiles with default images. Then you preview the remaining tweets and follow likely candidates for your product/service/. And besides that, the suggested app in the above post is dead anyway.