Anodizing dog tag like items can be held by titanium finger racks similar to what I have. These are available from most anodizing/plating rack companies such as vulcanium and servisure. These racks I have will hold 96 pieces per rack.
The Jump rings are anodized in a titanium anode basket where all the rings are tightly clamped together then when dyed, the pressure is released and a strong agigtation in the dye is used to cover up most of the connection marks.