My technique... When I make a nice post related to a subject that could interest one of my scientist friends or an ex collaborator, I email the link and ask my friend for feedback. I do not talk about Steemit, just send the link. For sure he or she notices the nice little number with the $ sign at the end of the post, triggering his interest...
I did this with my post on clathrate stars. my friend was intrigued by the site, he is a research director in French public research with strong entries to grand equipment (ESRF, LURE, ILL etc...) ... always good to have someone like this on board, so I hope he will look into it (and maybe his team ;-)). On my side, I will definitely introduce him to Steemit and SteemSTEM.