Yes! 4-5 hours each session in the sun. Lots of people think they'll be able to reverse 10 years of yellowing in one hour. It's not possible! It'll take hours and hours (if youre working on icy soles).
A suede eraser is normally used for this type of situation along with a stiff nylon suede brush. Use the Suede Eraser to rub the suede vigorously, then brush the nap using the Suede Brush.
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Flat Black will be your best bet. The color should be the same, but the amount of shine might vary slightly. Test it on a small unseen part before using if you're that concerned. Allow it to dry completely before making any judgements.
Hope this helps