Prepping ipe deck with aluminum spindles

Some websites say to just let ipe go to its natural gray patina and forget sealing but our ipe deck is getting some dark spotting that doesn't look good & probably isn't good for the wood. There is a little of the original Cabot Austrailian Timber Oil finish left on vertical surfaces--hardly any on the deck floor.

So I purchased Wolman's Deck & Fence Brightener to prep deck for staining & sealing with Armstrong's mahogany hardwood finish. Top and bottom rails are ipe with powder coated aluminum spindles in between. Wolmans says to completely protect aluminum from the cleaner to prevent damage. All I can think of is yards of Saran Wrap for protection, but that will only work on the middle--not where spindles attach top & bottom directly to the wood. Is there a solution besides unscrewing the many spindles and reattaching them after cleaning?

I also have painted Hardi board enclosing sides of the ipe steps that probably should be protected. Is there any cleaner/brightener out there that can do the job without damaging aluminum or paint? (If so, I'll return the Wolman's.)

This is a great website. Any help is greatly appreciated.