I just got call for an interview from my boss, while I was a visiting student from abroad. He offered me the position.

Very easy, just need to go through Professor. Very quick process. University helps with visa and all paper work. You need to be prepared to spend few days by exchanging the e-mails. Visits and choosing also possible, but you would need to cover expenses by yourself. In general recommended and nice interviewing. No stress or stupid questions. No drug testing or similar.