Can I spray the mould directly onto my moulded cheese instead of putting the culture in the milk?

You can do this with white moulds and the recommended process to do so is; 

1. Dilute the sachet content into cooled, boiled water, together with 1% salt brine (you don’t need much water, probably 1 Tbsp and a pinch of salt)
2. Stir well until fully dissolved
3. Spray onto your cheese
4. A prepared dilution should be used on the day of preparation, it won’t keep as the mould will die