The Tavern

Let's say you have a character who trained short blades to min delay, but now you want to switch over to using a long blade. Do you train long blades directly? Or do you train short blades to get long blades up to your desired min delay? Or do you just not do it and stick to short blades the whole game?
Aptitudes factor in so it also depends on race. For this example let's say halfling.

You train long blades. It does not depend on aptitudes or anything. Crosstraining is proportional to the amount of "skill experience points" you put into the skill you train. It is always better to train the actual skill you want.