Use a compliant backing so the abrasive can wrap around the curve: a leather strop loaded with compound, or sandpaper laid on a mousepad or a folded towel. Stroke edge-trailing, away from the edge, and let the soft backing maintain the convex shape rather than grinding a flat bevel into it.
A flat stone naturally grinds a flat bevel. Use one on a convex edge often enough and you will convert it into a flat grind by accident, losing the toughness the convex shape was there for.
The fix is a surface that gives. Compliance is what lets the abrasive follow the curve.
Lay wet-and-dry sandpaper on a mousepad or a folded towel. Stroke the blade edge-trailing, spine leading, with light pressure. The soft backing bulges up around the edge and abrades the curve rather than a facet.
Progress through grits, then finish on a loaded leather strop.
Kept up with regular stropping, a convex edge stays sharp almost indefinitely and rarely needs a full sharpening. That is its real practical advantage, and it is why axes and machetes use the geometry.