This is the standard (and traditional) polishing compound for gold.
If you are using a polishing mop, wait until the polishing wheel is spinning (a soft cotton buff), hold the block of rouge against it, the rouge is very soft and comes off onto the buff.
By hand: smear it onto the cloth, rub it on the jewellery firmly, don't worry if you get 'red' all over the jewellery, just wash it off under running water when you've finished.
Another tip: to polish fine scratches in glass (nothing too deep, e.g. if you can feel it with your fingernail it's too deep) smear it onto a fresh very clean very soft buff on a polishing motor and polish gently on a very slow speed. This is how it is used in the Motor Windscreen Industry, so it should work on glass cabinets too. But go carefully, you are polishing out scratches not drilling for oil.
For more about polishing click here.
QUESTIONS & ANSWERSAsk a Question
What is the grit size of jewellers rouge
No idea! It's more like a compressed 'powder' than a 'grit'. Maybe if you looked under a strong enough microscope you could meausure it...maybe not.