I don't know what kind that "$79 chinese detector" is, but it's possible that it's an all-metal TR type. Those ...... unlike the powerhouse Explorer, will see through iron better. But in all other ways, they're lacking. Or if it is a motion discriminator of some type, it's possible that that user is just more skilled at knowing what he's listening for. I can take a cheap detector and out-hunt a guy with a better detector, if the guy with the better detector is a rookie too.
But assuming you're each equally experienced, and assuming that the cheapie detector is truly a cheapie with no apparent advantage over your Explorer, here's some setting suggestions: The fact that you mention the "constant null" tells me that you have blacked out iron, so that you don't hear it. Instead, try this: go to ferrous mode. Don't black out anything on your screen. Now you will be hearing everything, but iron will give the tell-tale lower tone. You may ask "what's the difference whether it gave a low tone.... and I passed it by ear, or a null, and I passed it that way? Am I not passing it either way??" But here's where you're better off to hunt this way in iron: By hearing both the iron and conductive targets in each sweep, you're more likely to make better judgements as to targets trying to "peak through".
I use my Explorer all the time in fluffy plowed fields filled with iron, can slaw, etc... I do great! True, fluffy air filled soil is not as advantageous as firmer settled ground, with less air. But that is true for all types detectors, not just Explorers.