How to cover a piercing in the shower?

Tilt your head so the majority of the shampoo isn't running over your piercing, rinse it thoroughly, and make your piercing the last thing you wash in the shower so you know it's free of any shampoo or conditioner.

It will be fine, i have 2 cartilage piercings and shampoo has never affected them, just make sure that after, you rinse all of the shampoo off of them and they have nothing like that on them, i would always shampoo my hair, rinse it out and rinse it away from the piercings as well then when i got out of the shower i would take a cue tip and just run it around the piercings a couple times to make sure it was completely gone

Tape it off with saran wrap. You're going to have to tape it somehow and yet it will be slightly painful when you take it off, but that's the only way. Pulling tape off doesn't hurt as bad as getting the piercing itself.

Ever heard of a shower cap?

You don't. Wash your hair like your normally would, and then rinse the piercing very well after you shampoo, after you condition, and right before you get out.

My experience is that people with helix piercings tend not to bathe, so there's that option.