I tried using milk a month after I recieved my S. purpurea ssp venosa 'burkei' ($5) bareroot in June. A week or so ago, I noticed that the plant has started to produce 5 new growth points! I'm not sure if it was from the milk though. I have an S. flava ($5) with 2 growth points come to me bareroot 2 years ago, and that year it made 13 more growth points; I didn't use milk with this plant. Unfortunatly the following year, one of the big original growth points and 7 of the young ones were wiped out by fungus.
Might be a coincidenc then.