The reason milk works, is because of s little thing called Lactic Acid Bacteria, or Lacto Bacilii. Spraying pure milk can help, but what you IDEALLY want to do is promote a healthy phyllosphere by encouraging tons of GOOD, STRONG micro-organisms. If you do this from early on, you will never see molds. If you want it to work FAST, you can culture relatively pure Lacto B at home. It might be a bit late now seeing as it can take a week or more, but here is the method:
Take a bowl, fill 1/4 with brown rice. Top up with water, leaving an air-space (CRUCIAL) of about 1/3. Cover the bowl leaving a gap for air. Leave this rice water in a cool, dark place, around 2 ft off the ground, for 3-5 days. The water will get a milky colour and perhaps smell a bit. Strain the rice out, keeping the water (this water is now rich in microbes).
Pour water into a new container, and top up with 10x the volume of milk. Leave this for 3-5 days, until the milk seperates into a layer of white curds at the top, and a layer of yellow liquid at the bottom. This process will beat doen most bacteria and the Lacto B will dominate completely. This yellow liquid is your pure Lacto Bacilii culture.
Strain off your curds and discard onto compost heap. You can use the yellow liquid culture as is, diluted with 20 to even 50x the volume H2O and spray on your leaves. Most likely you will have much more than you need, so here is how to preserve the live bacteria and keep it alive for further use: Mix the yellow 'culture' with an equal part 'sugar water', this is made using Blackstrap Molasses diluted with 1/3 water. This is your Lacto B 'serum'. Dilute with 20x volume water and spray on plants.
This will beat down most other bad micro-organisms as it is much stronger.
For preventative measures during your grow, add some Lacto B to a fresh-brewed compost tea and foliar feed, every 2-4 weeks.
To learn more about how to brew your own compost teas, visit this thread:
https://www.rollitup.org/organics/676040-total-noob-using-teas-i.html
To learn more about True Living Organics, try this one:
https://www.rollitup.org/michigan-patients/583341-so-who-here-growing-true.html
Read both of them in their absolute ENTIRETY. Don't skip a post or page. You will have the healthiest plants you have ever seen. These guys are my GURUS.
Take care, and kick that mold's ass brother!