If I can't quite finish one off I use a Sudoku Solver site.
They are good- they work even if you just put the initial pattern in.
I haven't tried this but maybe it'll help you finish
http://www.solvemysudoku.com/
This one defintely works well
http://www.sudoku-solutions.com/
There is a forum that gives all the answers for PMU comps- save s a lot of time if you don't enjoy doing them.