I think the glossy acrylic coatings like super sheen have their place, but I don't care for them much on EDC working sheaths.
Depending on the dye you use, it can leave the leather with a hard, dried out feeling...this is the case with the Fiebing Pro dyes. A light coat of NFO will rejuvinate the natural oils in the leather but I wouldn't use it as my final finish...plus, too much and it tends to make the leather lose it's firmness.
You can use many premade finishes that work really well in weather proofing and protecting the leather. Montana Pitch Blend, Sno-Seal and even Kiwi Mink Oil (the paste) rubbed in makes a fine finish. Or, you can make your own finish using equal parts beeswax, paraffin and NFO. That's what I use, currently. It leaves a nice matte finish and I have no qualms about taking my sheaths out in the rain or snow.
I take my mixture and heat it up till it has just melted then leave very very low heat under it to keep it liquid. Then I take my sheath and heat it with a hair dryer or put it into my toaster oven, on bake, on the lowest heat setting (I think 140). You want the sheath to be fairly warm, but not hot enough to burn you. I take a small paint brush and paint on the mixture on the warmed sheath, you will see it start to soak in immediately. I put on a fair amount, till it starts to not soak anymore then place the sheath back into the oven. As it heats back up the leather draws in the rest of the mix. I do this a couple of times depending on how dry the leather was to start and how dark I want it to get. With black, no worries about darkening. But if I've dyed a nice light brown, the wax/NFO mix will darken it a fair amount.
Also, to help with dye bleed, make sure you vigorously buff the piece with a towel after the dye has dried to remove any residual dye pigment left on the surface. I use a microfiber towel for this, seems to work well in catching all the little nooks and crannies.
