So to make sure the edges are nice and even, I've masked off the top and bottom ready for a spray. Note the use of elegant masking materials and techniques:
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The Metalcoat says to do two light coats followed by a medium one at 10 minute intervals, so I give it a crack. it all goes really well except for a small run on the underside of the top horn. Hopefully I can smooth it off with some sanding in a week or so once it's cured.