I've been through all of this, and sympathise completely. First off you have about as good of a chance of seeing both sights, and the target clearly, as you do seducing a Victoria's Secret model. So the next best thing is seeing your sights clearly, and having the target a little fuzzy. So first off you need to get rid of the barn door in the Grand Canyon Patridge style sights if you have them. You virtually never see these on antique rifles, because they require your eyes to measure the amount of light on each side of the blade, which your eyes can no longer do. If you have a real understanding optometrist like mine, he will let you bring in your Longrifle so he can really get it right.
A gradual V rear sight, culminating in a round bottomed notch, with the center of the sight thinned to reduce glare, and or shadows, is the trick. The front sight should be a bead, or barley corn, that is a different color, but not reflective like brass, or silver. Make sure the rear sight is in the optimum spot, to get the clearest sight picture. Now let the gradual V draw your eye, and consentrate the focus, so you can put the bead in the notch, and put it all on the fuzzy bull, and squeeze the trigger. For me this is about as good as it gets.
Hungry Horse