Jack,
Gunnar has some really good videos on the subject, and he taught me a lot by them and reading his suggestions. But he's right, move the DD & DL in really small amounts - it makes big differences - they are potentiometers and that usually means they are not on a straight-slide scale but exponential. But the buried coins taught me a lot - that 10", 11" 12" dime taught me what adjustments to make and how the DD and DL work. Once you figure this out, it will be pretty easy for you.
Gunnar has a good video about swinging the detector like a pendulum; it works, so check that out too. I think you are gonna like the Blisstool. Though the settings interact with each other, it's not as hard as it looks - kind of like the GT, all those sounds to figure out.... but then, it starts making sense, and you will know what needs adjustment. Keep an open mind too. I'm a slow learner, so it took me somewhere between 10 and 15 hours of actually using it, between the test garden and real hunting situations. But that was from watching the videos and reading others posts. I learned how to try different kinds of things. It's a pretty fast machine, and it says to me "dig" or "don't dig", but there is no in between the two.
Good luck, and let us know if you find out a different approach to GB, and any other methods of using it. I like it a lot. It's not my only detector, but I have to say, it's the deepest one I own.