It is a 90:10 sand soil. But make sure that it is kiln dried. The dampness in the bags I used makes it much harder work and it doesn’t flow into the hollows so well. www.dandys.com/products/topdressing-sand-soil-mix
Silver sand is super easy to get hold of, it's the same stuff you use in kids sand pits, its definitely not the best stuff to be using. If you can get it you want kiln dried sports sand, if not grit sand washed and screened to 2-4mm is your next best best.
