While this is a great idea, there's an issue with it. These are payware assets from a third-party which means that the sessions will be extremely limited to only those that own those particular models, meaning the scope of the session is really narrow. Generally, with that said, sessions are broader and contain readily available assets. You can always edit any session in the Session Editor and replace a consist with another.
If you want a K&L-specific session, look for the one created for Coal Country route by Scratchy. This is a payware route available either from Jointed Rail or from N3V. This session requires you purchase the PRR D10s to haul coal on the route. There is a similar passenger session available for Scratchy's Eagle River.
Creating a session is not difficult and a lot of it is just time consuming. Before doing anything "creative" do a simple session with Drive to and Drive via track mark, Navigate to and Navigate commands will work too, to direct your AI drivers. When you get past the simple stuff like this,you can start making more complex sessions use more of the outlier commands and rules. You'll find that once this is mastered, everything else fits in between.
When creating sessions, you need to do a small bit at a time, stop, drive and test, then continue. For my very large Ozark Valley and Western route for example, I broke the route up into divisions and I used the Schedule Library to organize the driver commands into these subdivisions. Writing out the driver name, route, and destination first before adding in commands will give you an idea where you want the driver to go. In summary thinking, being organized, and planning ahead is the biggest part of session writing.