Has anyone successfully cleaned Birkenstocks?

[WanderingWisteria]

I have two pairs of Birkenstocks and the footbed of both is filthy so, after doing some googling and watching some YouTube videos, I have just got stuck in with the bicarb & water paste. OMG! The footbed is now a dark grey/black all over rather than just being an imprint of my foot. I have basically smeared the dirt all over the footbed. What do I do now? I have one done one shoe so far but feel I need to do the same to the other shoe so that they are at least equally dirty. Any tips appreciated!

This person did a great job: https://www.reddit.com/r/Birkenstocks/comments/rjpwo4/birkenstock_clean_up_wip/

"i used suede gum, sanded it down with fine grit sandpaper, and then washed it with diluted suede cleaner from amazon!"

I use the sandpaper method too.

Just do it outside and then wipe away any residue with a damp cloth.

Are you sure it's not just still wet?

I cleaned my Birkenstock dupes with the bicarbonate and water paste and left them out in the sun to dry for a couple of hours, then brushed the dried bicarb off. It completely took any smell away and made them feel much fresher and drier- but is it possible to reverse all discolouration?

Sandpaper ordered! Thank you