It has been rainy, but the coop doesn't turn into the mudhole it used to.. her crest is more just unsightly than anything else and I'd like to clean it. She's not very tolerant towards being held or manipulated. She hates having her head touched and its hard enough for me to get her to hold still enough for lice/mite checks. The waterer is a hanging one with that 1 inch dish all around and I don't think she can really get her crest in it.. although knowing chickens, they'll manage to do what ever you think they can't. It's just wierd how she only gets half of it dirty and the other half stays fluffy and moderately clean.
How does she get it muddy? Is the ground muddy or dirty? Is it just from drinking water? Does it rain often? Finding the source is the first step into solving the issue, otherwise, you can always clip the front feathers of her crest carefully, or tie her crest up in a hairtie, or when she does get it dirty, just get the front a little wet and work the dirt out with your fingers. If she's good, this should go through pretty well. If not, I best suggest you evaluate just how dirty her crest gets and if you should bother trying to clean it, or just do something like clip it or fix the source of the dirtiness.
My Polish can get their crests dirty but only in the winter when things get mucky, exceedingly rainy, and, well, dirty. To solve the issue and also the simple feeling of one's head burdened with a heavy mop, I clip the front feathers. Haven't shown any birds yet so it isn't harmful. During the slightly drier seasons I let them be, either clipped from winter or not. They may get a little dirty but nothing terrible.