ALERT! I don´t promote my posts very much, but I understand I important it is, because I have a degree on Economics and Marketing is one of the main keys to succeed at anything in today's world (as long as it needs others to buy/read your product/content).
Answering directly to your question, the best methods to have feedback on your Steemit posts is to share them inside the community, and for that there are not many famous ways (like instagram or facebook) to do it, but Discord groups are a very good way to share your posts.
I said the best way is to share them inside the community, because outside there are still too much ignorance and people are scared of visiting your posts outside the "usual" sites they visit.
I couldn't agree more; it's hard to attract people from outside the community, but think it's not impossible. The thing is that because they are not part of the community, and thus can't vote or comment, it's hard to keep track of how many people you actually reach with external promotion.
I think SteemIt should be implementing a traffic analytics feature.
Since you have a degree in marketing, don't you think it's frustrating how limited the options are when it comes to reaching a broader audience?