To answer a few questions:
- procure preserves the roe and adds color...I don't think it has any add scent designed to attract fish
-big spring eggs are one of the best eggs in IMO...they are so pale that they really color up well and I think that often color is a key factor whether its roe, wool ties, etc. I have caught fish on all species of roe except sockeye but htne again I have never tried it. A funny example... Bug pumper and I have had such hot days on the cap that we have run out of bait...we then have been know to clean our little cap coho and used chunks of those tiny cap coho skiens with pin sized eggs and had just as good results with that uncured roe as some nice procured spring roe!
-no one really knows what spefically will trigger an individual strike...we all kinda have an idea in general but I think a fish's "taste" are as individualized as we all are so every strike probably has different causes based onthe indivudual fish. that said, try and offer as many stimuli as possible ie, scent (roe or some additive), color (with a cure or contrasting wool with bait), etc.
-is the eggs natural scent enuff...yes but many people add scent for the reason above.
-every batch of eggs I cure seems to get a variety of results in terms of how quickly they milk and stay on the hook. Maturity of the skien and how tight it is plays a major role in an egg clusters durability...milking on the other hand, I am not sure what influences that.