Tropical Brown granite

We have recently had Tropical Brown granite slabs installed as kitchen countertops.  They were originally quite shiny, but now are dull and show every fingerprint.  We have asked the installer about maintenance, and have been told to only use GranQuartz 113M spray cleaner.  We've asked about using a sealer (which I do not think is required), but he never provides a straight answer.

 

So, here are the questions:

1. Should a sealer be applied?

2. What types of cleaning products should be used on a daily basis?

 

Appreciative of any advise...JAY