Congrats on the merc!
I use zero mode and all metal and custom. I don't touch coins mode. I'm mainly on the beach.
With all metal, I set the iron audio to 35 then shut it off. When I get a signal I like, I turn the iron audio on to investigate further.
In zero mode I don't discriminate. I'll look at anything that reads 38 and up or mid-tone on up.
I have custom mode set to discriminate 35 and everything else notched in. When I'm in zero mode, I'll flip to custom mode, turn on the iron audio. Helps a lot with bottle caps and deep rusty nails.
I try to use all metal mode because it's way deeper and is kinda like using my PI.
But I'll change it up when I know I'm in fresh-drop territory.
Hope that helps.