Cleaning climbing holds

What's the best/easiest way to clean holds?

What kind of holds? Gym holds that can be washed? natural hold? A good stiff plastic bristle brush works pretty good in most cases.

When it's time to really clean my holds, I use a 50/50 mixture of water and 5% cider vinegar in a bucket. I submerge the holds for a couple minutes, scrub with a plastic brush, and then rinse with water. They look pretty much new after that.
I always wear rubber gloves when doing this. The acidity of the vinegar is rough on the skin.

Dishwasher - someone elses is good :)

In the gym that I frequent they soak holds in vinegar/water mixture, scrub them, and put them through dishwashing cycle. Results are quite good.