unfortunately the best way of getting the experience you need is to get your boat out on the cut.
taking someone else's boat out will give you experience of how their boat handles which is not what you need, you need to know how your boat handles. my suggestion is to take the boat out (slowly and carefully) and find a empty bit of canal, then experiment with your boat (learn how fast it picks up speed, how fast you can stop it if you have to, how it turns at various speeds, how it reverses etc etc) all of these things will be unique to your boat and could be quite different to a seemingly identical boat.
You may be able to find someone to go out on your boat with you but they would be trying to learn how your boat responds at the same time as trying to teach you