How to overcome my resistance to lecturing?
I don't enjoy lecturing either and yet my student reviews ask for more lectures even if I prefer discussion. What I've done for some classes is prepare a portfolio of 15 minute mini-lectures that are on one specific point, targeted, succint, and within the attention span (maybe) of 18 year olds.

You might also want to create a similar grab bag of canned material so that when a particular topic arises, you can easily lecture on it. 

Otherwise, the only other way is to practice. I've realized my own aversion to lecturing is something I need to work more on, so I deliberately designed a large lecture course that was 100% lecturing, rather than the smaller seminar courses that I prefer.