Great fabrication job. I've found that yellow powder coating is like yellow paint, it needs some sort of primer underneath. My preference would be a flat white powder primer. I would think you can spray paint right over the powder coat; but I'd try a small spot for compatibility.
The manufacturers of Cardinal powder coating products make rattle can touch up paints; so that might be an alternative if the powder coater used Cardinal and a distributor is near you.
If you intend to completely respray the blade, I'd scuff up the gloss somehow.