I don't hunt with an F2 but spent all last year with its cousin, a Discovery 3300 by Bounty Hunter.
Your answer is really quite simple. Dig everything not iron! Especially all nickel/pulltab signals for gold and all high tones for silver.
There is no magic setting. I think you will do better hunting in All Metal mode and just ignore iron audio, or if that gets to be too much, disc out iron completely and dig everything repeatable regardless of which direction you swing.
Trash metal and rusty iron will give one way signals or jump all over the place, A gold ring or a silver quarter will not usually do this unless it is heavily masked by something.
Dig all nickel/tab signals and all high signals and you will be rewarded. I promise!! You may have to dig a few hundred pulltabs but eventually one will be a gold ring!
Remember that large metal objects will invoke a high tone, so judge target size by pinpointing. If it pinpoint the size of a hubcap, it probably is a hubcap!
Unless of course your on private property, then it could be a cache of silver coins!!
GL & HH...diggindad