Part of being an instructor is expanding your depth of knowledge and figuring our how to convey that knowledge to your students. That means you have to study the material as hard or harder than your students. I'd be a little careful about soliciting feedback from someone that is not an instructor. That is what your instructor is for. He or she will be the one to tell you if you got it right or not. As far as practicing your delivery, just practice out loud using what ever AV tools you would use for your class. Very few people are born comfortable speaking in front of groups. As you practice and get really familiar with the material your comfort level will increase. It's all part of the challenge of becoming an instructor.

When I was adding CFII to my CFI certificate the FAA had just added GPS approaches to the Instrument Rating PTS. My instructor told me to do a lesson plan for GPS approaches and teach it to him the next day. I didn't know much about GPS approaches at the time so it took me almost two days of research and writing to come up with two lessons plans. One on how the GPS system works and another on how to fly GPS approaches. Afterwords my instructor asked for a copy of my lesson plans because he didn't have anything for teaching GPS either. When I sent my first student up for an instrument check ride he performed a GPS approach during the check ride. Afterwords the DPE said "That's really cool, that's the first GPS approach I've seen".

Keep plugging away on those lesson plans and your presentation and check your ego at the door. Good luck.