Welcome! I was giving your question some thought and I think maybe the keyword here is credibility, not promotion (yet).
Breaking into this profession is very much, in my own experience and that of my close peers, a growth of trust-building and credibility in ones body of work over a long period of time. And it's something we never stop, primarily because every day we are building new relationships with others and facilities/studios (even if we've done the gig already for 5, 10, 15, or more years), and we want to nurture those relationships properly by putting our best foot forward always and having a reason for them to call us back: our bottom-line credibility. In my opinion it's a profession of daily first impressions. Much in the same way a financial miss step can affect a credit score, the same holds true for a miss step here too - it affects credibility, which at the end of the day is what gets out name out by word of mouth and gets many of us work. So to that end, focusing on credibility correctly means that the credibility will speak for itself and promote itself through your body work without you having to do a whole lot but get the job done.
It may sound harsh, but when we all start its a blank slate - nobody knows anything about us, what we're capable of, if they can trust us (both in what we can do, and how we can be trusted under not breaking NDA conditions) how well we can deliver on time, and so forth. Basically, we're in a place of being a huge risk for an employer/contractor - so I believe the first goal is to work toward reducing the risk.
By credibility in our work I'm speaking in the sense that, if you/I were hired onto a feature, are you/I capable of meeting the expectations of what's needed for that show? Can you cut hot car chases or combat sequences? I'm just using this as an example. But overall by credibility I'm referring to having developed credible sound editorial skills and a trained ear/sensibility. Nobody does right at the start, but that's why we all have (or likely have) begin in internship situations where we can increase out credibility by learning the ropes and being granted more and more opportunities on actual shows to help out, to the goal that one day you're running the ship and the show is your own.
My suggestion would be to look toward that route, anywhere you can be to learn from peers in the trenches, hands on experiences where you have some degree of a 'buffer' to help you out as your learning. It's all about learning, and finding somewhere to voluntarily intern like a studio (as well as taking on short films on the side to put into practice what you're learning at your internship) is a great way to begin to develop credibility in a body of work so that your developing credibility is doing the promoting itself.
These are just my 2 cents.