Still can't find a job after many interviews

Dear Career Doctor,

I am 29 now and have been working as a project,customer service engineer for 7 years in the manufacturing field and trading field. My education background sounds pretty poor. I only have a Engineering Hi-Dip from Local U and a BSC from a Australia University. I was being laid off at the end of 08 from a local manufacturing company, but I was still lucky at that time as I could still find a sales engineer job from a very famous trading Co.

I really did not think I am suitable to being a sales, thus I quit my job on last Sept and went to Australia with working holiday visa to try my luck there.

I came back to HK on end of Feb and I had around 8 interviews since then, unfortunately, all of these jobs are sales oriented job. I completely knew that I am not suitable to do sales job. I had to send CV to apply sales , since I found that there are not too many feedback from the manufacturing field and I think I do need to practice my interview skills, otherwise, I cannot perform well when there is any chance from the m