Hi rae_stl,
Fungal control with milk is different pH factor than a lacto-bacteria cultured product.
Use any milk you got (including powdered, goat, non-fat) diluted with water - you want it applied so that it coats everything lightly.
There are all kinds of formulas on strength. As for a specific milk's fat content, it is only a question of diluting enough so that leaf surfaces do not get too thickly coated.
Equal parts (1:1 or 50%) is for flagrant fungal crisis, 1/3 milk + 2/3 water if you are spooked, 1 part milk to 9 part water (10%) is commonly used for early control, minimal for routine preventative touch up sprays would be 2% milk volume.
Kefir pH is for humans. Spare kefir grains (being a symbiotic culture & not purely yogurt lacto-bacilli) might be an interesting experiment to introduce in a limited amount into a garden plant's root zone (to see if it improves the soil micro-flora to improve yield/resistance).

gringojay, thanks for the advice! I've heard of burying old SCOBY's, the kombucha culture, to raise acidity in the ground, but not for the bacteria, and haven't thought about the kefir grains. It makes sense though. Would the lil' buggers raise the pH do you think? They're really not sour, in fact they're pretty neutral. Hmmm, I may try this if the milk fails and the toms are keeling over anyways.

I sprayed with neem, but I read some posts saying neem isn't all that effective in the later stages of blight.

It's not. Neem really isn't a fungicide. It's use as a fungicide is primarily due to it's being an oil. Horticultural oils can 'seal up' attachment sites making it more difficult for fungal spores to attach and infect and they can also smother existing spores so they can't develop. As such neem and all oil products are best used as a preventative rather than a cure. Now, is it that milk encourages fungus that curtails blight, or is it that it encourages bacteria, specifically lacto bacteria, which does the same?

Some of the questions you are asking go beyond my knowledge so I won't comment/speculate and risk leading you astray on those, but will speak more generally.

There are competing theories as to why milk seems effective against some fungal diseases on some plants. To the best of my knowledge it was first found effective against powdery mildew on grapes, but was subsequently tested against powdery mildew on some other plants and found ineffective or inconsistently effective. It has also had some testing for other fungal pathogens with mixed results.

Corn meal is another means of controlling fungal pathogens. In this case it is suspected that corn meal, for whatever reason, attracts/feeds trichoderma fungi which are mycoparasitic and kill *some* other fungi. There are even commercial strains of lab bred trichoderma (T22 aka root shield is one). However, results are inconsistent.

That's the primary problem when biological controls or substances meant to attract biological controls are employed. The biologicals require fairly narrow environmental parameters to work effectively and there is no way to guarantee nature provides them when/where needed.

Hi rae-stl,
Please see 3 July 09 post on this forum titled "Yeast & Soil" for kefir curd reply.