Tank plating is the most ideal because the plating is even and heavier. But it is impractical if not impossible to tank plate while the furniture is still on a pen, so we pen plate.
You don't need to tank plate nickel. You can brush/pen plate. Just chose your solutions carefully. Clean well with a good surfactant to remove polishing compounds and oils from your skin. Be sure to rinse well with distilled water before plating. ....and yes, you should nickel plate everything before the gold plating goes on.