Millingtime, the explorers (of any of the generations of them) are VERY sound specific. Unlike other machines, and other brands, where printed instructions will tell a person how to do it, and a few air tests will cement the procedure, the Explorer is much different. Since it's got such a wide array of tooty-fluty sounds, which tell so much, you simply have to have someone show you. No amount of printed instructions (or tips/advice you can read on a forum) will do you any good. It would be like this:
If you asked someone "please describe the sound of C major to me, in printed text". It can't be done. It has to be heard/seen. Printed text can not convey a sound. So it's the same for the Explorers. I too tore my hair out, and couldn't understand how people were saying this was the latest greatest Whites killer (I couldn't debate their results in the field!). Finally, in disgust, after thinking "this is nuts! Everything sounds the same!", I met up with a proficient Explorer user in the field. This guy was effortlessly pulling silver dimes from the turf routinely at 8" and sometimes deeper! But to me, everything sounded like a flock of sick geese! But after having him flag a few suspected deep silver type turf signals, and watching the way he swung/wiggled over them, and after he pulls out his headphone jack to show me the sound he's trying to isolate, only THEN did the "lights go on" for me.
There is a totally different swing/wiggle technique for the Explorer, verses your old MXT. And the sounds are totally backwards too. Ie.: a "good" sound on your MXT, may not necessarily be what you're wanting on the Explorer, and vice versa.
So your best bet is to hook up with a proficient Explorer user (ie.: not just a sand box hunter, but someone who routinely comes in with the oldies and deepies). Have him flag some signals, both good and bad, and watch what he's doing, how he's swinging, what he's hearing, etc. And if he says "I'd pass this one", ask why. If he says "I'd chase this one", ask why. And you might even consider a headphone splitter (available at Radio shack) for this.