TweetAttacks is excellent and the free software version is good and comes with an easy to follow PDF. You can set your parameters and follow people in your niche and find people with large following in your niche and follow their followers with the TweetAttacks software. TweetAttacks Free Software Mark
I'm pretty sure that there's no subsitute for gaining followers organically. Any followers you pay money to gain likely won't be that interested in your services.
I would not use software to get followers but I will do it manually to get followers and get those same followers to like you because they see you tweet on a constant basis then they will tell their followers to follow you and their would do the same
If you go to twiends .com you can buy seeds and it users will follow you. (you can find more information on their website). I've used them before it works pretty well but you have to learn how to use the site as it can be difficult at times.
My expirience also from usgin other software to run accounts is pretty positiv ad most of them allows you to change times the software is working in which will make you look human If you are interested we mabe should talk via PM