From a tech who fixed our old mastrena constantly:
Scraping with metal is BAD (it scores the wand amd ruins it quickly). Soaking with too extreme of temperatures can also be bad for the temp sensor. Especially dont steam into a cup of ice water.
The "right" way:
Remove outer cover (can go in dishwasher)
Wrap metal wand with fresh sani rag to soak for 5-10 min, then scrap with a hot lid (should be easy after soaking) then you can use a paper clip/sandwich label for the holes.
MASTRENA 2 people: the wand is designed so that milk cant go up the metal side. All you have to do is run the cover in the dishwasher and wipe the wand with a sani rag.

I heard that you’re technically not supposed to use anything other than the blue scrubby, but people at my store would just use the metal scraper.

Soak in hot water and a tablet, in a venti cup, while cleaning the other parts. Then scrape gunk with two wooden stir sticks or plastic knife. Wipe off with a towel or blue scrubby.

Ok so, I know this is incorrect (as many things are from store to store) but we use hot water and a pill in a double cupped venti cup leave it there for a few mins and then come back and scrape with a gift card.

We take off the outside part, soak the metal in ice water, and use the hole of a hot lid to scrape. Works like a charm

we soak it in a venti cup of hot water and scrape it off with a spoon

Are you scraping the outsides?? Like do people not wipe after each steam? My store wipes them every drink and steams with nothing on it for a second or two, so there’s never really gunk on or in it at the end of the day. We just wash them like normal, no scraping needed 🤷🏼‍♀️

I think I read in the manual somewhere that you can take the outer part off and put it in the dishwasher. As for the inner part, my store soaks it in hot water (although the manual says you shouldn't do that). Not sure if this helps, but that's as much as I know 🤷‍♂️