One approach, of course is dubbin. As you all know, the specific rough-out on these boots was developed during WWII by Horween in collaboration with the Marines. Since the inside of the boot is natural CXL, the leather is impregnated with oils, making it incredibly water resistant. Soldiers would wax their rough-outs - referred to as 'dubbin'. In a conversation with Nick Horween, he told me, "Troops used to slick the rough-out with dubbin and the underside of an old fashioned glass coke bottle"
Pretty fucking rad.
The other option - and the approach that I think most people will take, will be simply to use a brass wire suede brush. This gets dust and dirt out of the nap to keep it clean.
Keep in mind - rough out is TOUGH - it's not like suede that we use for example on our navy suede trail oxfords. It's a different beast - one that is meant to take a beating
I think I like the 2nd approach more with the brass wire suede brush. What conditioner or weatherproofer would you recommend? Venetian shoe cream?