Stick with it.
Also I would say get in there as much as you can you never know when something will turn up.
The trick is to get your trial flights good. Especially if its a young wannabie. Include there parents, take time to answer questions.
Trial flights are your way of selling yourself to the student. And don't be afriad to give them a hint like I would luv to be your instructor but company says .... But i am sure as a customer you could insist.
When I left my full time FI postion I instructed mainly to keep current so all I did was trial flights and apart from a few problem cases which needed an new sense of humour thats all i did. Problem was after about 3 weekends I had nearly 3 ppl's wanting me as an instructor which i didn't want to do.
So keep the trial flights fun don't go for huge briefs ( I must admit I virtually gave up on them for Trial flights apart from the safety equipment) they stop listening in about the time you have asked them where they want to go. Let them do as much as is safe inside your safety envelope. I think my record was 16 trial flights in a row without touching the controls. You can sell a PPL just by letting them do the landing. It dosn't have to be pretty just the plane in one piece. And don't correct everything and talk at them all the time, as long as your not about to die or bust some airspace let them wander and generally make an arse of it.
MJ