One of the major benefits of a good IBL script is that it effectively organizes the experience of students so that their effort does not need to be used on such organization. A good script leads from very humble beginnings straight through the heart of a subject, hitting all the high points organically…hiding these high points in very harmless looking and natural problems. Students need only worry about one problem at a time, and the entire subject opens before them via their efforts.
Although there are good textbooks for teaching students about IMO/Putnam type exam problems, I don't know of one with the property that if a student worked serially through it he or she would efficiently pick up the necessary techniques and experience to become proficient. I'd like such a source that has the above IBL flavor, in that it is comprised of a series of individual problems to be tackled in order, with each problem innocuous-looking but revealing, in an appropriately graded way, the main tactics and techniques. At the end of the sequence, if completed, a student should have vastly improved ability in solving such competition problems. Is there any such source?