This is a great technique and really gives a card pizzaz.
It is amazing how it works--you have this wooden applicator that you put a felt square on to and you drop different coloured inks onto the felt plus a fluid that helps them to spread (I forget what it's called) you then pounce the block over your glossy card and end up with a beautiful mottled background which you can then stamp over.
I used a Stazon ink pad to stamp with -which is designed for shiny surfaces.
The first 2 cards were done in this style.