Of course this is only two samples, and it could have nothing to do with the vita-chem and everything to do with the pellets I sometimes feed (NLS), or the way I keep my water. I would need a couple dozen more fish from the same spawn with half getting vita-chem and the other half not in order to really test that. And unfortunately I don't have that much room yet. :D
As for how I give it: I think the best way to give it is to put a couple of drops on some frozen/thawing bloodworms or brine shrimp. I also add a touch of garlic juice to enhance the flavor. Then I use tweezers to feed. If however, frozen isn't your thing, simply adding 1-2 drops daily when you drop pellets in works as well. I like to put the drops right on the fish as they eat the pellets.
I do strongly believe it is worth using vita-chem. Other than providing a very welcoming, clean environment for my little fish Spooky to grow up in, I think that feeding her whole food (frozen bloodworms and brine shrimp) fortified with vita-chem is what caused her to become such a huge fish and develop the spots and colors she did. In using it with my male, who is much older and a rescue, the results are less dramatic. I attest this to the fact that he is already past the period where he is developing color and size, and because he is a dark color to begin with. However, in the 6 months I have had him, his dark black body has begun to develop a beautiful blue sheen starting at the dorsal fin and spreading towards his head. His dorsal fin has also started to develop salamander spots.