Rubbing alcohol with paper towels and q-tips, making sure you get all the
threads, post holes, and nooks and crannies.
O-rings are hardier than you think. As long as you don't pull them out with a knife, you should be okay. Keeping the rings dry makes it easier to remove IMO than if they're already wet with water or
juice or something.
After the good rubbing with rubbing alcohol, a damp paper towel (and maybe some more qtips) and a good wipe to make sure the last of the gunk and alcohol is gone.
I don't know why people think that soaking a new atty is going to clean it. There might be some misconception about metal and floating... it doesn't. Most of the gunk you find in a new atty is metal shavings with machine oil/lubricant holding it together. You have to agitate it and even pick it out with a toothpick sometimes. Soaking it in soapy water does not equate to magic.
(unless you're a pony with a rainbow tail that... okay I'll stop)
Good luck with the cleaning and I hope the bad taste goes away!