Well written post @crypto.piotr.

From my experience resteeming and mentions unfortunately don't work. Seeing post in a feed usually doesn't encourage to visit it (unless it has catchy photo or title), and if the post is resteemed the probability is even smaller.

I think that memos are the most efficient and not so bad way of promotion - as long as users agree to receive them. Unfortunately the system of "messages" as a memo on Steemit is broken in my opinion, because contacting with people through wallet interface is terrible experience, at least for me.