Best products and process to polish piano black KEF speakers

You are going to want to create a virtual system. Click on you user name a couple times Dashboard and Virtual Systems. I can never find it directly... I always have to fool around with my user name and Dashboard before you get a long list including virtual system. When you get there it is easy. 

Maybe someone actually knows the direct route.

Without pics it's impossible to make recommendations that are not guesses...but assuming you have swirl marks and minor scratches in the clear coat only, so far only the suggestion by @bigtwin is on the right track (other than contact KEF). Waxes and polishes  wont help, even though products like Zymol genuine carnuba waxes are very good at protecting surfaces once corrected.

Menzerna also makes very good paint correction / polishing products.

But true paint correction cannot be done by hand. You need a professional grade machine, not a cheap rotary polisher you might find at Walmart.

A proper auto detailer might be a cheaper alternative to buying the materials and gear, and acquiring the skills to do this, unless you already have them.

@rayray57   go to imgpile.com and upload any picture.  Then right click and copy image location.  Click on the picture icon in the Audiongon post menu bar.  Copy the image address into the url line.  Picture will appear in your post.