I did the last bits on my other fence. Painting 40+ meters of 12mm round bar is going to suck.
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As suggested, I would get that galvanised. If you don't like the shiny finish cover it with high build vinyl paint after etching the zinc with a wash. A mini hvlp spray gun is great for round bars, you can set it for a narrow spray pattern so you have little overspray. You can get adapters to fit a full size paint pot on them.