How did you find your agent?
Selecting the manufacturer can be quite daunting. I've recently been sourcing a decent T-Shirt supplier in China. You can go to sites like Alibaba and Global sources and find thousands of factories that offer T-shirts. You contact them and they will send you prices for basic Tees but when you start talking distressed or vintage wash the communication dries up quickly.
Whilst they can manufacture anything you've got to be very specific with your requirements. It takes time but try to find a manufacturer who is doing similar garments to your requirements. When I started my Teddy Bear Business I went through over 100 suppliers and agents to find one that could make a tightly knitted hooded top for the bears. I've seen many copycat offerings since I started but none come close. I'm lucky to have a really excellent agent in China who checks all my mechandise and although I pay a little extra I sleep better! Ong gave a really good breakdown but sometimes you can be as detailed and as specific as you like but if they have a problem understanding your requirements you are banging your head against a brick wall. If it was easy everyone would be doing it. You got to be prepared to stick your neck out you are ordering 1000 pieces per stlye per colour, you've got to get it 100%.
My Chinese is non-existant but my agent speaks better English than me, that helps!