Whirly,
we are/were all keen to full exercise our new found instructor skill, not to mention our ability to be paid to fly. However, I think that starting by doing the "odd" trial lesson is really a pretty good way of starting. It gives you time to develop your own technique (no amount of "teaching" an FI instructor is a substitute for teaching a real ab-initio student / trial lesson customer).
You also have time to reflect upon what you did last time, before you get your next victim. Before you know it, one of "your" trial lessons will turn into a full-blown PPL student, and away you go..........
I still miss doing TLs - seeing the pleasure people get from a simple hele flight - Enjoy it!!