After seeing my

use her water bowl to try and bathe in, I tried many things to help her. She got very angry with the spray bottle and yelled "NO! NO! NO!" at me (I think her previous owner used a spray bottle to punish her). I tried taking her in the shower and she really didn't like it and was panicked. I set up a special area with a large baking dish and she wouldn't go near it, no surprise here, she is a gray and is naturally scared of new things.
What I have found is that I really can't force her to bathe without her freaking out (I probably can't force her to do anything, fortunately I rarely ever have to try since she is usually cooperative... unless it involves water, her harness, or new parrot toys/perches).
My recent solution that worked:
I put out that large baking dish again, but this time on a table she normally plays on and surrounded table with towels on the floor. She ignores it at first. She wont go near it when I try and encourage her. Skawks at me when I splash her. Eventually she will go there on her own, throw out the toys I put in it to entice her, and then spend the next 2 hours dancing, singing, and splashing her way to a fun time making a complete mess and getting water everywhere.