From: Lorane, Pennsylvania, USA
Once Objective planning reaches 100, units can use training to increase in experience. Sometimes, it's better to leave the planning objective unchanged even when moving the unit elsewhere for low experience units. Experience from training is limited based on unit nationality. There's a table in the manual. It ranges from 45 to 65.
Non-combat units as you say, probably refers to units that cannot attack. They can still gain experience from defending in a contested hex.
I have been inputting my orders for the campaign game first turn since July 4, 2009. I'm getting close. In another month or two, I might be able to run the turn!