My brand new deck with composite decking/rails was just finished late last fall. Of course the 6x6 support posts, the outer beam, and the stair stringers are pressure treated lumber. My GC told me to wait until this summer to stain/seal them. What should I use on them?

Also, I think I may cover the 6x6 posts in vinyl cladding. Should I still treat the posts first before covering them up?

thanks

Steve