i work saute / fish station at my restaurant and i work with a 6 foot stainless steel le plancha as we call it.
Keeping the damn thing as clean as possible is always the issue, what have i learned after 2 years? scrape... and scrape and scrape all the fcking time. Every single time you have half a second to breath? scrape it with your tool. Generally if it works for an hour, and then stops working in my mind it means you aren't doing it often enough and / or the blade on it needs to be replaced.
The reason why it's slowly turning black is because a small layer of oil is burning on top. Scrape and wipe (i don't wipe but it could help)(if you got some semi clean hand towels that you can use to grab things out of the oven; thus not using extra clean towels)
I love my chef, that man does a lot for everyone when he can. But working in this business i know ordering sht can sometimes take forever, new blades? i ask for them often and when i know friday is coming and i got a dull blade that just isn't working out, i leave the house an hour early, hit up home depot and buy the blades myself, I get a receipt and when i actually have time talk to the chef about getting refunded.
We don't use bricks, i scrape, use some degreaser, let it cook on there really nice, then use a 8-12qt container with big ice, and flip it over on top of the plancha, move it around to quickly cool down the plancha and it practically cleans it self, i might use a metal spatula to throw the melting water in a corner that i need it, Do this twice, hit it with suds and wipe twice, finish with cooking spray on top and wipe it with a dry towel.
Also keep your all your semi-dirty / moist hand towels until the end of the night , use them to clean the inside oven doors or the oil traps in the plancha during service to avoid using 100000 towels during one service.