Well, I prefer Selcon to Zoecon,(quality) and Zoe to Selco(quantity), so I use one of each brand. Zoe is heavily based off algae (spirulina and kelp) and indeed has some more vitamins/minerals that Selcon doesn't, calcium, magnesium, Vitamin A, etc. Selcon is based heavily of highly unsaturated fatty acids (marine lipids) that isn't in Zoe (plants/algae don't have much fat lol). Selcon contains a bit of Vitamin C as well, however I use Kent's MarineC daily.
As far getting the supplements on the food, here's what I do, prepare everything going into the meal (angel food, silversides, krills, scallops, etc) into a shot glass. Let that sit for about 45 mins, then put it inside my freezer. That way I can make an entire weeks worth of food one time, using different shot glass for each daily meal. Then when I use it, take it out of the freezer, let stand for however long it takes to thaw out and then strain the water out. Merely dunking the food in the supplement for 5 mins won't allow any marinating to happen and they'll just wash off once the food hits the tank.
Sep, so ya, basically Zoe doesn't have the fatty acids. I am fairly sure Vita-chem has both types of supplements available, vitamins or fats. I think they may label them one for freshwater (fats) and one for salt(vitamins). No sure what is going on with bergamer's angel either. The only thing I know of is he has not been feeding any sponge food, I'm really unsure how vital that is to proper angelfish health, but pretty important, I would assume. I don't know what else wild angels eat besides sponges and tunicates