Hopefully Calabash and some other experts will chime in soon. Since you are already familiar with Field 2 (Park 2 is very similar) you could set it up anyway you like or just leave it alone. You could set up a nickel/lead/gold ring and high conductor US coins/silver notched program in Park 1 or Field 1 since they are similar too.
Iron nails and old iron bigger than coin sized can break through discrimination settings and sound off anywhere on the numerical and audio target ID range depending on depth and size. So you have some choices. The 600 allows you to turn iron volume way down so you can barely hear it and you can even change its pitch and the numerical range for the first tone break. So you could hunt with Field 2 wide open, no discrimination and just audibly deal with the iron while having a notched Field 1 or Park 1 when you need a break from the iron tone barrage. Or you could also add a little background threshold tone that will go silent over discriminated targets and hunt with your normal settings that you are used too and if you hear the threshold tone nulling (going silent momentarily) around what sounds like a good target, hit the horseshoe button and check for iron. Of course, you could use your regular settings with no threshold or iron volume adjustments and then expect to dig a lot of iron that shows up as non-ferrous or you could check every target with the horseshoe button before digging.
Jeff