I may not know the secret to selling lots of books. But what I do know is what doesn't work. The hard sell is definitely one of those things that doesn't work anymore. "Hard sell" means a direct "try my book out!" sales pitch posted/said anywhere.
When I first started publishing about a year and a half ago, I was at the tail end of this tactic still working. As in, I could go on Facebook, offer to gift copies and then reasonably expect one or two people to take me up on my offer. But this doesn't work anymore. You could say your entire collection is up for free forever and it would land on deaf ears on Facebook.
Same goes for Twitter. If I had a penny for every author posting book links, I'd be a lot richer than I am selling short stories. This type of approach doesn't work if you're an unknown author and it really doesn't work if you're an unknown short story author.
And don't think "well it doesn't hurt to have those buy my book auto tweets, it takes no effort and there's always the chance..." It does hurt you. A lot. Because the people who actually read tweets start to ignore you. They learn to associate that anything with your name by it is usually just a sales pitch. It would be better to just not tweet for the day.
Find other ways to attract attention. Don't tell people to buy your book. Make them want to buy your book.