1)The video doesn't show acid washing but it shows some basic stuff.
2)No idea about hydro film ink. It might work if the ink is UV resistant if not it will fade out really quickly. Rit dye does the same thing looks great but after a few trips outside the part begins to lose color due to UV exposer.
3)To acid wash you anodize then dye a piece. Then use either bleach or acid or both to remove color. How wet your piece and the type of bleaching agent used when your removing color gives you the soft organic type lines your talking about. A high polish finish on the part prior to anodizing it also helps.