They will in both places. Its pretty simple, you just fill in a form after you disembark the plane, then go through a screening area which has thermal camera's on you. Ad's about 10-20 mins to checking out time but in both Beijing and Tianjin airports it was pretty efficient (i just got back on Monday so this is a recent experience), so no reason to think Guangzhou or HK will be any different.
I only saw one person nabbed, and that was out of literally hundreds going though in Beijing. That was a little kid that wasn't coughing or sneezing either.
I was totally stressing out about it beforehand for no need. Don't sweat it, its very unlikely its going to be a problem for you.
Just one thing, they do want a phone number on the form of a contact in China.
If you don't know your ladies phone number just put your hotels reception number would be my advice. They are very careful about checking out the H1N1 forms so if you leave this out they will kick up a fuss.