In reply to joljols:
If it's really bad he should talk to his GP, there are medical options.
That said, it's probably more manageable with a bar towel and a well stocked chalk bag than you/he thinks. I sweat a lot, especially indoors but I've learned to cope with it.
If he's just starting out it's likely to feel like a much more overwhelming problem than it actually is since it'll be stacked on top of all the other things he's having to learn to cope with. Once things like tying in, planning moves, placing feet, staying in balance etc etc are more comfortable and habitual he'll probably feel more able to take a hand off to dry and chalk it when needed.
In a hot wall I'm chalking my tips pretty much every move, drying my palms as and when I can hang about a bit longer. In some ways smaller holds are a blessing since you only need to dry your tips!
jk