When to use brightener

I have a deck with a semi-solid stain that I am going to remove. I don't know what brand of stain it is as the previous owners did it. I will be using Restore-A-Deck stain stripper (with a power washer) to remove the stain and then sanding to remove the remainder and staining with TWP 100. I would like to know if I should apply the brightener prior to or after sanding the wood.

Thanks for your help.