Years ago, I went through the pasted obsession and pasted most any fine gritty substance from slurry, pigments, cleansing powders and metal polishes, on a variety of substrates.

They all work, to a degree and depending on what you are trying to achieve, polish vs edge straightness/comfort.

The problem with using slurry is, you do not know what the grit is or size. As opposed to using known grit, of known size. These days I use Chromium Oxide, Cerium Oxide, Diamonds, Metal polish, (3m or Maas) and CBN. CBN the most, almost daily.

If you want to experiment paste cardboard, inside of a cereal of shirt box, it is inexpensive and most like leather but easy to acquire and inexpensive if it does not work.

Also with any paste, results will vary dramatically, with the substrate. Leather is very different from Balsa for example.

But, and most important, if it is working for you… Rock On.