Gon
You and Gon bathe together but he's used to it. At first, Gon requested you wear a bathing suit because he was uncomfortable with you being naked around him. Now he's fine with it but you only bathe together occasionally whenever your at his house. Afterwards Gon likes braiding your hair.
Killua
You and killua bathe together too!! Usually Killua will want to shower instead, but you don't like showering with other people. You just prefer baths or showering by yourself. Killua respects your decision and you usually talk to each other while he's showering but 9/10 he'll want to bathe with you and you end up on either sides of the tub. Sometimes you help Killua wash something idk. Afterwards you both lay down somewhere and turn on any given fan on the the fastest setting and see how long it takes to air dry 😈.
Kurapika
Kurapika works long hours and usually afterwards mopes around by himself thinking about random things. Ever since he met you though, you've always made Kurapika bathe with you. Kurapika got super shy looking at you so now he sits behind you. Sometimes he helps you wash your hair and he takes a long time doing it because he likes playing with your hair. Sometimes if he's in the mood he'll leave small pecks on your back which always make you squirm. Afterwards you help each other dry your hair.
Leorio
I can't imagine Leorio taking a bath. Sometimes you shower together and he helps wash your hair. You just sit back and observe.
Hisoka
Hisoka doesn't care if it's a shower or a bath. He'll always choose to be with you but sometimes you make Hisoka choose the other option so you can relax by yourself.
Illumi
Illumi doesn't shower... idk what he does. I can imagine one scenario where you drag Illumi off and bathe him while you wash and brush out his hair. If your feeling extra you'll even leave tiny braids throughout his hair. Illumi never takes these out and won't unless you redo them.