Tea coins (mini cakes) - how to brew?

Hi all – I have some dancong tea coins (from White2Tea) and I’ve found them challenging to brew with. They’re super-dense and very small (7g of leaves), so hard to break up dry without basically powdering the tea to pieces. But when I added the coin to the gaiwan and started to soak / wash – it remained a (soggy) cake – even after several washes. But I didn’t want to leave to soak for too long for fear of spoiling the tea. How do you approach tea coins like this?
Thanks!