Yes you should dampen hardibacker before setting to it,
and as has been mentioned, there's not reason to use
quick setting thinset unless you have to. Why a salesman
would sell a DIY'er quickset- I don't know. Quickset materials
rarely last more than 10-15 minutes despite what the directions
say. I only use it when repairing a few tiles in a high traffic
area that is difficult to keep people/animals off of for more than
a couple of hours.

thetiler