In disc go to 40 or below on the gain, 30-35 would even be better.
You actually will still get pretty deep, (the power range in this thing is not actually 1-99), but even using a bigger coil target resolution gets better and this seems to fool your detector into thinking you are using a laser-like fine sniper coil and targets will pop up like there are little red flags over them.
I have used this a bunch in areas that frustrated me like in heavy iron or massive trash like around picnic pavilions.
Pretty shocking when you see this happen in the field.
Don't know why this works...it just does.
I use this method mostly in heavy trash, for extreme iron I found a different method that works even better, I call this the Blast Through Method.
https://metaldetectingforum.com/showthread.php?t=196462
It is the opposite of that low gain way of doing things but again...on Fisher units hunting in heavy iron more gain actually gets you even better resolution than lower gain which is opposite thinking using many detectors.
The high beams don't work near as well in fog as lower beams way of thinking.which on Fishers this is just not true.
This is a real thing, NASA Tom knows it because he has commented on this technique in the past and as I continued to use it over the years I got better and better at it and found tons more in sites so infested with iron you would be shocked.
It also works in heavy mineralized dirt shockingly well which I have in spades.
This is my number one way of hunting here when I pull out my Fisher.
It took awhile to get used to it and learn to notice the exact the behavior I am looking for but now it is second nature to me and I have been super successful using it over all other methods.
Motion all metal, turn the gain all the way up to 99 and max out the threshold, too.
Not sure if DST will affect anything so try it on and off and see.
I use the F70 which doesn't have that so with no DST less filters I have to work with, (or against), and this method works fantastically great without it.
It will be ultra jumpy, schizophrenic and noisy, the biggest part about learning this method is getting used to all that but if you can, and once you do, the sky is the limit.
Use any coil you want but move slow, watch for a range of numbers that repeat, not just a few like using regular disc but more like a range of 6 or so.
If you get big drops out of that range way lower as you slowly move the coil around a small area just move on but if you can keep it with that smaller range then see if you can get the same behavior coming at the target from a different 90 degree direction.
If you can great but not done yet, you need to make sure you are over an actual target and not just getting a false high tones being thrown off by iron in the vicinity that will happen often using these settings.
Notice the area where the target seems to be and move the coil away then hit the pinpoint trigger then move back in to target center.
If there is no target at that area but one seems to be a few inches away this is going to be iron falsing in that target area so move on.
If there is a target in that exact location and you continue to get that higher range of numbers that aren't dipping down into iron dig that target...it will most likely be something non ferrous.
Might be something good like a coin or it could be something else but there should be a non ferrous target down there that might or might not be near actual iron but something else besides iron should be down there.
Get good at this technique and eventually you will be able to identify non ferrous targets at will no matter how much iron you are dealing with.
Sounds weird, totally different than what most of us know as hunting normally but if you can wrap your head around it and learn to hunt this way in iron your skill set will be enhanced greatly and it will pay you major dividends going forward.
It sure has for me for years.