I tried hard also to define the proficiency level of soft skills when I was making a skills inventory matrix for all employees. Then I came up with 4 levels of proficiency, i.e.:
0 : Doesn't understand & doesn't apply (in daily work)
1 : Understand but doesn't apply
2 : Doesn't understand but apply (by nature)
3 : Understand & apply
Hope it will be useful for you.
12th May 2011 From Indonesia, Jakarta