Yes, but not a very good one, as when they're bigger they'll start charging you the instant they see the dish. Target training them with a bell or ball on a stick would work much better.
Small ones will always be shy about eating in front of you, as they grow they will become much bolder. A 6' nile isn't going to be scared of you whatsoever.
As far as the sexing, it would be wise to note that the method has only been used on Australian and geographically close species, not on African species, and even in some of the species they did it to, the juveniles were not sexable. The only larger species tried was V. spenceri, nothing else. It could work, but I wouldn't use it as a definitive method.
If you want to breed and want to take a gamble that they are in fact both females, I'd grab another baby.. If you don't raise them up together, breeding them will be tricky unless you have a gigantic cage that adult niles can hide from each other in, as unsocialized adult niles will behave nastily towards each other.. Even ones raised together may simply kill each other if they don't have a big enough cage, introducing adults to each other would be almost a guarantee of murder.
) at the next show if I don't see any hemipenes between now & then. I might even give the illumination a shot at the show if the vendor is willing as it would be nice to try it on a larger sample size just to see if it's a usable sexing technique for this species. This "little" project seems to be getting bigger & bigger every day. 
