Also, please teach me the canned air and hammer technique. I predict Queens is going to experience a rash of industrial site breakins soon 
Quite simple. Have you ever read the instructions on those cans? Have you ever wondered why it says to never invert the can?
Well, I have and Google being my friend, I was amazed by the results. It turns out that using the can inverted lets the chemicals flow out of the can in liquid form. Being decompressed rapidly, those liquified gases drop in temperature to -40° instantly. So, if you spray the stuff inside a padlock it will make all the internals somewhat brittle. All that's left to do is hammer it open.
But if you want a gentler way, just google "padlock shims". This won't break the locks but also doesn't work on good quality locks like those made by Master.