I have only had experience with charm packs.
A friend told me to place the charms in a large bowl of hot water , (no detergent). I put a Shout color catcher in the bowl as I had some lights and darks colors in the charm pack. Soak charms in hot water for about 5 minutes. If you see the water turning colors, refill the bowl with water until it stays clear.
Next, get a salad spinner,(the kind you put lettuce in to remove the water after rinsing the lettuce) Place the charm squares in the salad spinner and press the spinner to remove the excess water from the charm squares. Hang the wet charms to dry. I put mine over a clothes drying rack stand. Putting in a dryer may distort the charms or cause fraying.
Some people separate the charms into light and darks and place in separate bowls to test color fastness. Good luck