question about sealing

I have granite countertops, 3 years old, Labrador Green (but very 
dark and almost black).  Which one of your sealer do you recommend?  
I use Marbamist to clean them every few days, and have sealed them 
twice, but they just don't seem as shiny and slick as they did when 
they were new.  I'd love to order some of your products, but can't 
figure out which one to get.  I read many of your posts, and you are 
full of info, hope you can help me.

Thanks,
Jane Palmer