When I got my FI rating, I phoned round all the flying schools in my area. Most said no, but one said, "I don't need anyone, but you're welcome to drop in for a coffee if you like". I did, trying to look the part, and doing my best to make a good impression...."I may not have done any flying instructing, but I've worked with people all my working life", etc etc. He then said he'd like to help me, and if I could find my own students I could teach them on his helicopters. So I advertised, wrote articles, put up cards, talked to people, and so on. I got a few takers, though no-one carried on for long....but then the school started giving me the odd trial lesson. And then when I next phoned around, I could say I had experience......
Keep trying, keep networking, grab at any straw you're offered as you never know where it'll lead. Good luck.