Here in a nutshell is what I did to fix up our neglected deck.

1. Apply paint and finish remover.
2. Wait for it to work while keeping from drying out.
3. Used a stiff brush with handle to work old opaque sealer up.
4. The stripper didn’t do much for me, so…
5. Powerwasher, 2,600 PSI, I know enough to damage wood, but it was in such bad shape anyway.
6. Let dry.
7. Pound down all nail heads, replace or fix screw/nail pops.
8. Sanding boards with 6″ Random orbit sander (60 grit).
9. Sanded railings and other details with 5″ RO sander (60 grit).
10. Blew off dust with leaf blower.
11. Take a step riser board to the local paint shop for an expert review of what I had on there. I didn’t remove all of the original stain.
12. Applied Sikkens Opaque deck stain.
13. Done.

Here’s my article with photos that might help in more detail (I’m just a homeowner, not an expert): Refinishing a Pressure Treated Deck