My favorite video that demonstrates the old style, as well as the evolution of second line, is New Orleans Drumming. One clip, in particular, from the video is performed by Herlin Riley who does a beautiful job of demonstrating the traditional form:
There is a segment by Johnny Vidacovich who diiscusses (and demonstrates) not only the second line style, but other New Orleans music which was derived from the roots. This clip of Vidacovich is not from the video, but does contain some of the techniques he discusses in it, with an emphasis on the all important clave rhythm:
The late, great Earl Palmer is also in the video. He discusses the influence of New Orleans drumming on popular music of the 1950s and 1960s. Palmer is one of the most recorded drummers in history, along with Hal Blaine, so it is illustrating to discover how pervasive the New Orleans and second line influences are to contemporary (for that period) music.
The final segment is performed and discussed by Herman Ernest, who shows the influence of early New Orleans drumming on funk.
If you want to dig deeper into the art of second line drumming I recommend Stanton Moore's A Modern Approach to New Orleans Drumming, which may be more in line with a more modernized approach to learning the style. Moreover, Moore's DVD is more focused on instruction, making it a great learning tool.