I don't use them. I guess it is because my walk speed changes. For winter rye, I'm full open. For small seed, I measure out the amount of seed I want in the field based on acreage and load it. I then start with a small opening and make a pass to ensure full field coverage and then make a second pass with it open a bit more. It is probably not the most efficient way to do it but it works. When I first started, I tried to use and record settings. For whatever reason (probably my walk speed variability), I would sometimes run out of seed before I finished the field. That left me with a field that was too thick in spots and empty in others.
My first two passes are methodical. If I have seed left after the second pass, I zig-zag around randomly with the door open even wider.
Thanks,
jack