In the factory Coin mode, all Iron will be eliminated.
Junk that falls into the "accepted" area is aluminium, screw caps, pull tabs, ring pulls, juice lid foil caps etc
You can easily reject a lot of the above, but then you will start to reject other good stuff as well.
All locations are different, some are loaded with aluminium foil, others pulltabs. So you start detecting, dig everything, and then after a while you will see what the
common junk target is. Then you can make a decision to reject it or not.
You can do this two ways:
1. Physically black out the screen where this junk target is coming up at
2. Just ignore the number range of that target.
I will dig everything or cherry pick depending on the location, how easy it is to recover targets, how much time I have, the age of the site etc. etc. You'll develop your own system and gut feel as you go.
Tonnes of good info on the CTX on Minelab's Treasure Talk. You can filter out by detector model on the left hand side.
Just don't try to absorb too much initially.
Nenad