I always advocate for using a heavy duty grease like THIS.
You use it the same way as anything else, it's just thicker and does a phenomenal job lubricating and protecting your bearings. You don't need a ton, just smear some into the bearings (obviously you would pull the cover off of them, but I assume you know this if you're going to be cleaning them anyway).
Everyone talks about different thinner greases and lubricants, but this stuff is seriously good, and a tub will last you a dozen lifetimes. There are smaller containers of the stuff if you don't want to spend as much, or have as large of a container. :)
Smear thick grease on the wall. This one is green, but there are neutral coloured ones too. No-one would want that on their clothes or hands.
I have been using this Lucas grease for the last 5 years (still have a about 75% of the tub) not sure if its optimal but it works for me.
https://www.amazon.com/gp/product/B000IG5QOQ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1