Hard ground

The ingredients you need to make a hard ground is:

2 parts (8.5tbsp) lump/egyptian asphaltum
2 parts (5tbsp) beeswax (white is purer but yellow works too)
1 part (3tbsp) rosin

An ingredients list isn't quite enough to stir up a decent hard ground. You need to know how to make it, too. I have never actually tried this and am mainly posting this as a future reminder to myself. There appears to be a decent recipe/method for hard ground in Practical guide to etching and other intaglio printmaking techniques By Manly Banister, starting around page 11.

Do you have any tips?