Manual takes too much time but to be honest, i go for both ! Manual and softwares as you can't replace a human
Sendible is best in my opinion because of the research that comes with every post. Automation is safe they are used by big brands to update all their profiles at once. Only bad tools are social exchanges like socialadr, youlikehits, etc because they are majority fake accounts and bots.
Hey Hanhash! There's a great site called Instant IG Posts, which is great for managing a business' social media. It allows to you to save time, grow your followers, & expand your social network presence. It is somewhat similar to Hootsuite, as someone mentioned above, but for INSTAGRAM! It has a few great features: 1) Allows you to schedule Instagram posts 2) Upload content from ANY device (in bulk, too) 3) They will interact & network on Instagram for you (This is the pro plan).... For example, I know if you are selling women's clothes, they will make sure your posts have the proper hashtags, as well as interact with possible customers, post & comment on other Instagram profiles in your target market, etc. Here's a link http://instant-ig-posts.myshopify.com
I suggest not to use any SMO tool. Do regular update and interact with your followers to get maximum value.
It is important not only to provide unique but also interesting content, do not copy other sites or blogs. Organize feedback with your users, post daily, luck!