I long since outgrew this but, every once in a while, I catch a bit of an old Gene Autry or Roy Rogers movie from the thirties and early forties on one of the cable channels. Inevitably, there would be two or three (or more) seques into musical interludes with players like "Sons of the Pioneers" or "Riders of the Purple Sage" to name two examples. The strumming technique on these old Hollywood "cowboy" songs is probably fairly close to what you're looking for. "Riders in the Sky" still does a lot of that kind of music.

As an aside, years ago, we referred to the old "boom-chukka-boom" sound (orchestrally) as the "businessman's bounce."