Lakeside PT wood deck In upstate NY

Hello Scott;

I am getting ready to restrain a large deck, 1084 sq feet built of pressure treated wood >35 years old, still in good shape, which was treated with Sherwin-William's armor seal treadplex (WHAT was my contractor thinking?) which is now peeling off. I fear you will recommend sanding to remove what is left, ~60% still attached.

Once clean of the "paint", what do you recommend? Shall I still strip and brighten before applying a stain? What stain do you recommend for this location? I'd like to go with a gray and of course want to get more than one year out of the effort! 
thanks!

-kathy