trouble using bondo

Hi all,
Sorry if this post is in the wrong area I did not know where else to put it.
Ok here I go.
I have welded in all the repairs, I have done the rough body work it looks pretty good but not perfect. So when I try to put a final coat of bondo on it looks like crap, I sand it down and try it again and the same results.
My question is how do I get it perfect? What should I do or what I'm I doing wrong?
Is there any body men in the Toronto who could maybe do the finish body work and maybe even paint in there spare time.

Confused in Canada

Rick