I dunno, Pete: I got the basic strum with thumb--and a few chords--in about an hour from Pete's book. A few weeks later I was doublethumbing melodies up the neck. As I considered myself primarily a singer, I was pretty satisfied--for a while. Then, like you, I found basic strum a dead end, moved into three finger picking--helped by Earl Scruggs book and record--and finally, when I began playing regularly with some old time music fans forced myself to learn to frail. It wasn't easy, possibly because of habits learned up-picking. And drop-thumb has been much harder to learn than double thumbing: again, because of my habit of reaching for the strings with my thumb. I went back to Seeger's book when I started frailing, fine--but my real breakthrough with drop thumb playing came from Dwight Diller's instructional video (his first one is aimed at intermediate players, but he supposedly has one out for beginners now.

But still, Seeger got me going.

--seed