First there is Pete Seeger's book which you probably already have.
There are now books, as far as I know, that is focused on up picking, but there are several that contains demonstrations and instructions of old-time banjo styles with up-picking, clawhammer, two finger index lead, two finger thumb lead, and old three-finger styles.
Art Rosenbaum have three books that contains Old Time styles: up picking, clawhammer (down picking), thumb lead (which is an up picking style) and old three finger styles:
Old Time Mountain Banjo (out of print but sometimes second hand are available at Amazon or ebay
Mike Seeger (brother to Pete) has made a three item DVD set, Southern Banjo Styles, where different old time banjo styles are demonstrated, including different up picking styles. Mike Seeger also has an earlier DVD set (one item) Old Time Banjo Styles which also contains demonstration of different old time banjo styles.