I am not even sure what you mean by scale counting. Thats usually done to identify one species from another, or in other species to tell sex but I have never heard of it being used for corns.
What scales are you counting????
Anyways the only methods available are:
1. Probe. Must be done by experienced person, entails the probe being placed into the vent. They count how deep it goes in, but you cannot do this with your eye. Most accurate method aside from breeding. *L*
2. Popping....done when the snakes are very young. Not always very accurate...but it works. Less accurate than probing.
3. Tail comparision. This is the LEAST accurate method and I wouldn't count on it....but the males tails are longer, and don't start to taper right away to the tip like the females do. A females tail is shorter, and starts to taper right after the vent ...to the tip.
Marisa