Great ink to have in your toolkit! I picked this up to use on sketch card commissions to add some shine to things like armour, weapons, spaceships etc.
Ive used it several times now diluted with water and a touch of india ink (and several of the other various coloured inks by TomStudio) to create various effects and shimmers.
Most recently used it as a thin layer topcoat on a sketch card of the marvel comics X-Man "Colossus" who's body is made of organic steel. It goes on easily, very smooth. I used a round no.2 brush to apply.