A fair amount of time (January 1970, so 8 years I guess) after the introduction, but in my memory* I recall Popular Mechanics ran a 2 part series on building an N-scale layout - hopefully this Google books link works: A lot of railroad in a little space. Back then (and well before) magazines like Pop Mech and Pop Science would feature stories on Model Railroading (or, OK, train sets - although some of the work they were doing in the 1920s would impress contemporary modellers - and boy did they know their radio-electronics then). Nowadays, the few times I read a recent Pop Science it was meh…
Don’t know about Blaze Starr and N scale advertising (well, OK, I’ve read about it), but in the late 1970s wasn’t there some suggestive ads from, IIRC, Patti’s Corner or something like that?
*OK, my memory’s not that good - I didn’t recall the issue when it was first published (as I was 5 or so). It was stored in the basement the early 1990s when Dad was convinced we had to toss the old magazines (which were getting a bit mildewed, and we suspected crickets were living among the boxes), so in cleaning up looking for cool articles to clip…well that’s where I saw the layout feature. Luckily many of the old (and cool) issues are available via Google Books.