In this video I show the method I use for track ballasting, plus I take a look at a ballast alternative that is 10 x cheaper than ballast products available in model stores.
https://www.bunnings.co.nz/egmont-pumice-5l_p00167620
Of course, the pumice is only suitable as an alternative for a similar colour ballast. It wouldn't work if you were aiming for a grey ballast appearance.