He's got a good machine that will flat out find the silver coins, but it's not a magic wand either. He has to put in the time to learn the tones. Tell him to be patient, move slowly, keep the coil flat on the ground, dig a ton of targets, and learn from each one he digs. Once the light goes in his brain his pouch will be filled with oldies.
For now tell him to stay in multi-tone and semi-auto sensitivity (set sensitivity to 26) set the threshold setting so he can barely hear it, then bump it up one number, make sure your volume is set to 10, Gain is factory set at 5 and I'm willing to bet your friends has been set higher. For now you don't want it set higher than 6-7. Variability I'd set to 9 or 10. Sounds: I started off using ferrous with my XS and Explorer 2 but came to the conclusion that conduct worked best for me. No matter which one your friend starts off with he should stick with it until he learns the tones. Then he can experiment by switching back and forth to compare the tones. I'd also start off with fast on and deep off, especially if he is in places with lots of trash. With fast on your tones won't be as sharp as when it's off but once your learn what to listen for it won't make a difference (in my opinion
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Tell him to Always go by tones first, then use the screen and depth to help him decide if he wants to dig or not. The key for now is to learn the tones and use good detecting technique.
One more thing is that I'd use one of the preset programs like coins to begin with then I would use as little discrimination as possible after I've learned the tones. I always used zero discrimination until I got my E-Trac.
Tell your friend good luck for me. Once he learns the Explorer he's going to dig a lot of silver.