You have two per algo, so by adding more algos you can have an unlimited number of advise methods for the same asset. "Long" and "Short" are just names, both functions behave exactly identical as to my knowledge. So you could use adviseLong for entry and adviseShort for exit, for example.

A way for generating an exit rule would be to write some code for classifying the exit by peeking into the future. In the training phase you can then pass the current classification value to the Prediction parameter at any bar.