I have tried loads of white pens over the months - from all over the place - China and the USA included. I have even tried white paint pens and - even nail painting pens. I have tried pump action pens - gel pens - roller ball - fibre tip - anything I could find. The only blank I have drawn is to get hold of a Sharpie white pen - I just can't get or import one from anywhere. Very strange that one - but there you go.
Anyway - we have progress - and I think I have cracked it!!!
The winner - the Signo White gel roller ball pen - It's amazing. Really wet and thick - you can gently tap it on for tiny spots and if you write over black it's smooth and consistent. I just love it.
I have them in the shop and ON LINE HERE.
Try one - you won't go back.