If you haven't, you should check out the Old Cardboard article written by two board members about this set. (Or just check out the article on Mike Peich's great website:
http://t209-contentnea.com/t209-overview/)
In my experience, Crockett, McGeehan, Wilson, and especially Hoffman are the easiest to come by. Pope, Sisson, Fullenwider, and especially Booles were toughies. Definitely Booles does not come up for sale often. The others are in between. But except for Hoffman, most are pretty rare. I would think that some people who have been sitting around for three years waiting for, say, a Lane would say Lane would be the hardest one, and they wouldn't necessarily be wrong. Takes some patience to acquire this set card by card.