he has to go out of canada and proceed with landing process. He can also do inland landing by going to local CIC office, but that application takes few months whereas at port of entry it would take only 10mins. If he's close to US border he can go out and come back in canada. If his passport belongs to the list of visa waiver countries in US then there should not be any problem, else he would need a US visitor visa to enter US even if its for 1 second.
for visa stamping he would need to send you his passport by mail/courior. Before he sends, he should make photocopies of passport and visa for security reasons.