Chromium oxide powder mixed into a thin slurry, something like the tip of a teaspoon handle with 3 rain drop sizes of water drop.
Use a paint brush to spread on the board. Also use the thinnest leather you can for your board the there is little give in the leather.
I have made hundreds of board using this method and not one complaint. Chromium Oxide is cheap as chip on EBAY
You can also use Auto sol which is very good, I have tried with hard compound but difficult to apply and the also did not have a perfectly smooth surface as with the other products .
If using Diamond steels some of the super steels might need 10 micron paste. And with all stropping you don't need to press hard.