If at all possible, I would suggest taking the time to dye the cross red and dying the belt black around it instead of painting it. The color may fade or change a bit over a long time, but it doesn't run the risk of being scraped off.
That being said, if you would rather go with paint.. test on scrap first. Sometimes paint has a problem holding to dyed leather. Most painting on leather I've ever done has been without dye underneath. A good acrylic is preferred, and I usually thin it out with some water, and apply in light coats with dry time in between. Gives a better overall coverage.
Another thing to consider, is if you're rubbing in the super shene and not using an aerosol, then you can possibly end up wiping the paint right off when you try to seal the belt.