MOMO Shifter, that is correct.  Our brokers can a

MOMO Shifter, that is correct.  Our brokers can and do loan our shares to shorts, and often do shorting themselves.

The concept of shorting is easy enough, and you are right, following the junk P&D newsletters would be helpful.  I have never been involved in stock shorting (I am told it is controlled by organized crime), but if your trader friend is doing this from Brazil, it might be interesting to learn how he does it.