I Don't know any trainers in WA, but a suggestion would be to select a couple & go & watch, look at the handlers & dogs body language, do they teach Positive Reward, etc.
One of the best tools we found when training our staffy lead work was to start with a NO PULL harness , this has a clip on the chest for the lead & when they pull it turns them back to you, after a few week we were able to go to a flat collar successfully.