Using iron mask gives you the ability to select how much iron you want the detector to hear. So what your friends are saying is that when you use a wide open iron mask screen, you hear everything the detector does. The more you open up the screen, the less discrimination.
Why do they suggest it ? Because it also makes the detector re-set much faster between targets and the NULL period between targets is actually GONE with a wide open screen.
The more rejection/discrimination ... the longer it takes the detector to re-set ( null period ) between targets.
Problem is ... for a newby, it's a bit overwhelming for the brain to hear that many targets together in a high target environment !!!
So what's the answer ?
It all depends on the user, because there are many ways to get good results by using discrimination, very little discrimination or no discrimination, it's whatever makes the most sense to you !!!
It all boils down to finding out what kind of site you're hunting, what size coil to use for best results, and of course, how you choose to set-up the detector .... and that will come with time spent in the field.
This site can be a great resource for answers along the way of LEARNING how to get the most of your Explorer ..... but there are no real short cuts that actually makes up for hands-on and taking short cuts may or may not leave you truly UNDERSTANDING what you hear from the detector in the field.
On a positive note, you already have some buddies that hunt with Explorers who can help you see, hear and understand by comparing screens, if they will take the time to do that it will help you more than anything you read here or anywhere else.
Whether or not you're using the smart find screen or digital is up to you. For some folks the digital is easier to learn and associate to in the field, especially beginners.
But ... for those that have spent many hours with the Explorer ... it doesn't matter because they are hunting by SOUND first and foremost because all of those sounds have CLICKED in their minds and they know when they hear what they are looking for and it stops them in their tracks when they hear it ... then ... they may look at their screen and start getting serious.
Anyway ... bottom line is .... the more you use it ... the more you will understand.
Good Hunting
Mike