All I've used is Fermaid-O, since I bought it ~2 years ago..
You'll need a decent understanding of YAN, so you might want to read
this and
this, if you havent already..
You'll need to guesstimate the amount of YAN provided by the must.. If it's just honey and water, then its basically a starting YAN of 0/zero.
So then you'll want to look at the yeast you're using, and the nutrient demand/requirements it has for optimum health.
I dont have time to do the math right now, but I can try to get back to this later this evening and help you out again.. But basically, there's formulas for figuring the YAN of the additions, and you'll need something like ~250 ppm (mg/L) for an average fermentation (low-medium nutrient demand yeast)..
So if you had an SG of 1.100, you have ~0.100 worth of movement.. Because fermaid-o is an organic nitrogen source, you can add it later in the ferment / the yeast will be able to metabolize it for a longer period of their life than inorganic forms..
You'll notice Seth and I differ a bit on our approach here, but they both work; I'm not scared to add Fermaid-O @ 1/3 sugar-break, where Seth normally stops @ 50% or so.. Also, he adds more of it than I do, I believe (been out of touch with winemaking for a bit myself, not as fresh as I should be).. So how does this translate to the 1.100 SG?
That 0.100 movement could be broke into 2 or 3 parts.. So you'd add nutrients every 0.033 or 0.050 worth of movement... The batch would start at 1.100, first addition is after the lag-phase / when the yeast form a cap (probably ~1.098 ish), then the 2nd addition would be either at ~1.074-1.050, and if the 2nd addition was at `1.074, a third addition would be @ ~1.040..
2 versus 3 additions though, the amount added would be different, just to point out..