Update - Ive been using 'Raincoat' visor repellent and it's the dogs!
As it's wax based the water just beads and sheds - you don't even have to do the 'head move' thing in the wind to shed the water!
It's been on there since Friday (5 days) and still as good as it was at the start of use.

I bought 2 packs (5 sachets per pack) which on predicted usage should last me unt the end of August.

Go buy guys and gals - it's a great product!