I made a few exit bags following the PPH guide before I finally turned out one I was happy with. I found it takes a bit of practice, but then I’ve never been real good at handcrafting things.
I haven’t seen the Derek Humphrey videos and I no longer have his book, however I do have Docker’s Five Last Acts which does provide some detailed instructions for the sweatband version. I tried making one with the band enclosed inside the hem of the bag (which seemed more secure rather than just taping it on to the end of the bag) and found it quite difficult. Hardest part was to keep the sweatband stretched to the same width as the bag while you’re attaching it.