There is a tiny plaque brush called GUM go-betweens that is used to clean plaque between teeth. I decided to try one to clean the gunk inside the mouthpiece. Worked great and was easy to use,but what came out was quite disturbing. I definitely need to clean more often. Walmart pharmacy has 8paks of the brushes for less than 2.oo and I'm thinking maybe some Scope mouthwash would work for a deep scrub solvent to dip the brush in.
I don't think I'd use mouthwash to clean a harp! I know there is saccharin among other ingredients in most mouthwashes. I don't know if that stuff would be good for your harp (might be sticky?)? I just use water, unless I take the harp apart, then I use Kaboom, some alcohol, and then water. I also have something called "Mi-T-Mist" which is a mouthpiece Cleanser that I used on trumpet mouthpieces, but I have yet to try it out on a harp? ----------
If your harps are getting real dirty and smell bad, I'd suggest not eating right before, and rinsing out your mouth real good before playing. Also, make sure to tap your harps out when you are done. If I know I'm going to be playing for a while (and I am at home) I'll brush my teeth before playing. After I am done I will usually wipe my harps down with a clean rag.
I used to snag myself extra wetnaps when I'd go out to eat at a BBQ place, and I used those once in a while. I also found that toothpicks work real well for scraping crud like dried saliva out from the holes and around the mouthpiece.
Here's a video in which Jason Ricci shows how he cleans his harps:
