Any of those things mentioned could work. Remember that the object is a liquid tight connection. If you don't have this you know what will happen.
"Basket" anodizing is common for small hardware. This involves a stainless steel or titanium basket (lots of holes in it) and a perforated lid with a means to tightly squeeze all of the hardware into good contact with each other. This leaves small unanodized patches where contact was made. This method also requires extremely vigorous agitation in all of the anodizing, rinsing, dyeing, and sealing steps.
(edited for correction)
All those things except just letting the hardware lay in a tray, a lousy connection is practically assured with that.
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