Further development... proving Lynn is right about prepping thoroughly...
The main problem was the old wax from the last owner. This had dried hard and white on the handles.
So yesterday I set to using a household mild liquid abrasive scourer (Jif), and applied it with a hard bristle toothbrush. I scrubbed vigorously, being careful not to touch the paintwork.
Rinsed the handles down, and result was magic!
All the white has come off, and the handles are dark - like their original natural finish. So it doesn't really matter whether I put any darkening agent over it... won't make much difference.
I was really surprised. Maybe I was too gentle in the past.
Ken Silver
--------------
1999 Mercedes SLK, 1999 Suzuki Grand Vitara, 1993 Mercedes SL500, 1991 Daimler (Vanden Plas). Finish detailing, then start all over again...